diff --git a/app/core/src/main/java/com/fsck/k9/Account.java b/app/core/src/main/java/com/fsck/k9/Account.java
deleted file mode 100644
index ba7c7ce6f..000000000
--- a/app/core/src/main/java/com/fsck/k9/Account.java
+++ /dev/null
@@ -1,1108 +0,0 @@
-
-package com.fsck.k9;
-
-
-import java.util.ArrayList;
-import java.util.Calendar;
-import java.util.Collections;
-import java.util.Date;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-import java.util.concurrent.ConcurrentHashMap;
-
-import android.text.TextUtils;
-
-import androidx.annotation.NonNull;
-import com.fsck.k9.backend.api.SyncConfig.ExpungePolicy;
-import com.fsck.k9.mail.Address;
-import com.fsck.k9.mail.NetworkType;
-import com.fsck.k9.mail.ServerSettings;
-import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
-
-
-/**
- * Account stores all of the settings for a single account defined by the user. Each account is defined by a UUID.
- */
-public class Account implements BaseAccount {
-    /**
-     * Fixed name of outbox - not actually displayed.
-     */
-    public static final String OUTBOX_NAME = "Outbox";
-
-    public enum Expunge {
-        EXPUNGE_IMMEDIATELY,
-        EXPUNGE_MANUALLY,
-        EXPUNGE_ON_POLL;
-
-        public ExpungePolicy toBackendExpungePolicy() {
-            switch (this) {
-                case EXPUNGE_IMMEDIATELY: return ExpungePolicy.IMMEDIATELY;
-                case EXPUNGE_MANUALLY: return ExpungePolicy.MANUALLY;
-                case EXPUNGE_ON_POLL: return ExpungePolicy.ON_POLL;
-            }
-
-            throw new AssertionError("Unhandled case: " + this.name());
-        }
-    }
-
-    public enum DeletePolicy {
-        NEVER(0),
-        SEVEN_DAYS(1),
-        ON_DELETE(2),
-        MARK_AS_READ(3);
-
-        public final int setting;
-
-        DeletePolicy(int setting) {
-            this.setting = setting;
-        }
-
-        public static DeletePolicy fromInt(int initialSetting) {
-            for (DeletePolicy policy: values()) {
-                if (policy.setting == initialSetting) {
-                    return policy;
-                }
-            }
-            throw new IllegalArgumentException("DeletePolicy " + initialSetting + " unknown");
-        }
-    }
-
-    public enum SortType {
-        SORT_DATE(false),
-        SORT_ARRIVAL(false),
-        SORT_SUBJECT(true),
-        SORT_SENDER(true),
-        SORT_UNREAD(true),
-        SORT_FLAGGED(true),
-        SORT_ATTACHMENT(true);
-
-        private boolean defaultAscending;
-
-        SortType(boolean defaultAscending) {
-            this.defaultAscending = defaultAscending;
-        }
-
-        public boolean isDefaultAscending() {
-            return defaultAscending;
-        }
-    }
-
-    public static final SortType DEFAULT_SORT_TYPE = SortType.SORT_DATE;
-    public static final boolean DEFAULT_SORT_ASCENDING = false;
-    public static final long NO_OPENPGP_KEY = 0;
-    public static final int UNASSIGNED_ACCOUNT_NUMBER = -1;
-
-    public static final int INTERVAL_MINUTES_NEVER = -1;
-    public static final int DEFAULT_SYNC_INTERVAL = 60;
-
-    private DeletePolicy deletePolicy = DeletePolicy.NEVER;
-
-    private final String accountUuid;
-    private ServerSettings incomingServerSettings;
-    private ServerSettings outgoingServerSettings;
-
-    /**
-     * Storage provider ID, used to locate and manage the underlying DB/file
-     * storage
-     */
-    private String localStorageProviderId;
-    private String name;
-    private String alwaysBcc;
-    private int automaticCheckIntervalMinutes;
-    private int displayCount;
-    private int chipColor;
-    private boolean notifyNewMail;
-    private FolderMode folderNotifyNewMailMode;
-    private boolean notifySelfNewMail;
-    private boolean notifyContactsMailOnly;
-    private boolean ignoreChatMessages;
-    private String legacyInboxFolder;
-    private String importedDraftsFolder;
-    private String importedSentFolder;
-    private String importedTrashFolder;
-    private String importedArchiveFolder;
-    private String importedSpamFolder;
-    private Long inboxFolderId;
-    private Long outboxFolderId;
-    private Long draftsFolderId;
-    private Long sentFolderId;
-    private Long trashFolderId;
-    private Long archiveFolderId;
-    private Long spamFolderId;
-    private SpecialFolderSelection draftsFolderSelection;
-    private SpecialFolderSelection sentFolderSelection;
-    private SpecialFolderSelection trashFolderSelection;
-    private SpecialFolderSelection archiveFolderSelection;
-    private SpecialFolderSelection spamFolderSelection;
-    private String importedAutoExpandFolder;
-    private Long autoExpandFolderId;
-    private FolderMode folderDisplayMode;
-    private FolderMode folderSyncMode;
-    private FolderMode folderPushMode;
-    private FolderMode folderTargetMode;
-    private int accountNumber;
-    private boolean notifySync;
-    private SortType sortType;
-    private Map<SortType, Boolean> sortAscending = new HashMap<>();
-    private ShowPictures showPictures;
-    private boolean isSignatureBeforeQuotedText;
-    private Expunge expungePolicy = Expunge.EXPUNGE_IMMEDIATELY;
-    private int maxPushFolders;
-    private int idleRefreshMinutes;
-    private final Map<NetworkType, Boolean> compressionMap = new ConcurrentHashMap<>();
-    private Searchable searchableFolders;
-    private boolean subscribedFoldersOnly;
-    private int maximumPolledMessageAge;
-    private int maximumAutoDownloadMessageSize;
-    private MessageFormat messageFormat;
-    private boolean messageFormatAuto;
-    private boolean messageReadReceipt;
-    private QuoteStyle quoteStyle;
-    private String quotePrefix;
-    private boolean defaultQuotedTextShown;
-    private boolean replyAfterQuote;
-    private boolean stripSignature;
-    private boolean syncRemoteDeletions;
-    private String openPgpProvider;
-    private long openPgpKey;
-    private boolean autocryptPreferEncryptMutual;
-    private boolean openPgpHideSignOnly;
-    private boolean openPgpEncryptSubject;
-    private boolean openPgpEncryptAllDrafts;
-    private boolean markMessageAsReadOnView;
-    private boolean markMessageAsReadOnDelete;
-    private boolean alwaysShowCcBcc;
-    private boolean remoteSearchFullText;
-    private int remoteSearchNumResults;
-    private boolean uploadSentMessages;
-    private long lastSyncTime;
-    private long lastFolderListRefreshTime;
-    private boolean isFinishedSetup = false;
-    private int messagesNotificationChannelVersion;
-
-    private boolean changedVisibleLimits = false;
-
-    /**
-     * Database ID of the folder that was last selected for a copy or move operation.
-     *
-     * Note: For now this value isn't persisted. So it will be reset when K-9 Mail is restarted.
-     */
-    private Long lastSelectedFolderId = null;
-
-    private List<Identity> identities;
-
-    private final NotificationSetting notificationSetting = new NotificationSetting();
-
-    public enum FolderMode {
-        NONE, ALL, FIRST_CLASS, FIRST_AND_SECOND_CLASS, NOT_SECOND_CLASS
-    }
-
-    public enum SpecialFolderSelection {
-        AUTOMATIC,
-        MANUAL
-    }
-
-    public enum ShowPictures {
-        NEVER, ALWAYS, ONLY_FROM_CONTACTS
-    }
-
-    public enum Searchable {
-        ALL, DISPLAYABLE, NONE
-    }
-
-    public enum QuoteStyle {
-        PREFIX, HEADER
-    }
-
-    public enum MessageFormat {
-        TEXT, HTML, AUTO
-    }
-
-
-    public Account(String uuid) {
-        this.accountUuid = uuid;
-    }
-
-    public synchronized void setChipColor(int color) {
-        chipColor = color;
-    }
-
-    public synchronized int getChipColor() {
-        return chipColor;
-    }
-
-    @Override
-    public String getUuid() {
-        return accountUuid;
-    }
-
-    public synchronized ServerSettings getIncomingServerSettings() {
-        return incomingServerSettings;
-    }
-
-    public synchronized void setIncomingServerSettings(ServerSettings incomingServerSettings) {
-        this.incomingServerSettings = incomingServerSettings;
-    }
-
-    public synchronized ServerSettings getOutgoingServerSettings() {
-        return outgoingServerSettings;
-    }
-
-    public synchronized void setOutgoingServerSettings(ServerSettings outgoingServerSettings) {
-        this.outgoingServerSettings = outgoingServerSettings;
-    }
-
-    @Override
-    public synchronized String getName() {
-        return name;
-    }
-
-    public synchronized void setName(String name) {
-        if (name == null || name.isEmpty()) {
-            this.name = null;
-        } else {
-            this.name = name;
-        }
-    }
-
-    public String getDisplayName() {
-        return name != null ? name : getEmail();
-    }
-
-    public synchronized String getSenderName() {
-        return identities.get(0).getName();
-    }
-
-    public synchronized void setSenderName(String name) {
-        Identity newIdentity = identities.get(0).withName(name);
-        identities.set(0, newIdentity);
-    }
-
-    public synchronized boolean getSignatureUse() {
-        return identities.get(0).getSignatureUse();
-    }
-
-    public synchronized void setSignatureUse(boolean signatureUse) {
-        Identity newIdentity = identities.get(0).withSignatureUse(signatureUse);
-        identities.set(0, newIdentity);
-    }
-
-    public synchronized String getSignature() {
-        return identities.get(0).getSignature();
-    }
-
-    public synchronized void setSignature(String signature) {
-        Identity newIdentity = identities.get(0).withSignature(signature);
-        identities.set(0, newIdentity);
-    }
-
-    @Override
-    public synchronized String getEmail() {
-        return identities.get(0).getEmail();
-    }
-
-    public synchronized void setEmail(String email) {
-        Identity newIdentity = identities.get(0).withEmail(email);
-        identities.set(0, newIdentity);
-    }
-
-    public synchronized String getAlwaysBcc() {
-        return alwaysBcc;
-    }
-
-    public synchronized void setAlwaysBcc(String alwaysBcc) {
-        this.alwaysBcc = alwaysBcc;
-    }
-
-    public String getLocalStorageProviderId() {
-        return localStorageProviderId;
-    }
-
-    public void setLocalStorageProviderId(String id) {
-        localStorageProviderId = id;
-    }
-
-    /**
-     * Returns -1 for never.
-     */
-    public synchronized int getAutomaticCheckIntervalMinutes() {
-        return automaticCheckIntervalMinutes;
-    }
-
-    /**
-     * @param automaticCheckIntervalMinutes or -1 for never.
-     */
-    public synchronized boolean setAutomaticCheckIntervalMinutes(int automaticCheckIntervalMinutes) {
-        int oldInterval = this.automaticCheckIntervalMinutes;
-        this.automaticCheckIntervalMinutes = automaticCheckIntervalMinutes;
-
-        return (oldInterval != automaticCheckIntervalMinutes);
-    }
-
-    public synchronized int getDisplayCount() {
-        return displayCount;
-    }
-
-    public synchronized void setDisplayCount(int displayCount) {
-        if (this.displayCount == displayCount) {
-            return;
-        }
-
-        if (displayCount != -1) {
-            this.displayCount = displayCount;
-        } else {
-            this.displayCount = K9.DEFAULT_VISIBLE_LIMIT;
-        }
-
-        changedVisibleLimits = true;
-    }
-
-    public synchronized boolean isNotifyNewMail() {
-        return notifyNewMail;
-    }
-
-    public synchronized void setNotifyNewMail(boolean notifyNewMail) {
-        this.notifyNewMail = notifyNewMail;
-    }
-
-    public synchronized FolderMode getFolderNotifyNewMailMode() {
-        return folderNotifyNewMailMode;
-    }
-
-    public synchronized void setFolderNotifyNewMailMode(FolderMode folderNotifyNewMailMode) {
-        this.folderNotifyNewMailMode = folderNotifyNewMailMode;
-    }
-
-    public synchronized DeletePolicy getDeletePolicy() {
-        return deletePolicy;
-    }
-
-    public synchronized void setDeletePolicy(DeletePolicy deletePolicy) {
-        this.deletePolicy = deletePolicy;
-    }
-
-    public synchronized String getImportedDraftsFolder() {
-        return importedDraftsFolder;
-    }
-
-    public synchronized void setImportedDraftsFolder(String folderServerId) {
-        importedDraftsFolder = folderServerId;
-    }
-
-    @Nullable
-    public synchronized Long getDraftsFolderId() {
-        return draftsFolderId;
-    }
-
-    public synchronized void setDraftsFolderId(@Nullable Long folderId) {
-        draftsFolderId = folderId;
-    }
-
-    public synchronized void setDraftsFolderId(@Nullable Long folderId, SpecialFolderSelection selection) {
-        draftsFolderId = folderId;
-        draftsFolderSelection = selection;
-    }
-
-    public synchronized boolean hasDraftsFolder() {
-        return draftsFolderId != null;
-    }
-
-    public synchronized String getImportedSentFolder() {
-        return importedSentFolder;
-    }
-
-    public synchronized void setImportedSentFolder(String folderServerId) {
-        importedSentFolder = folderServerId;
-    }
-
-    @Nullable
-    public synchronized Long getSentFolderId() {
-        return sentFolderId;
-    }
-
-    public synchronized void setSentFolderId(@Nullable Long folderId) {
-        sentFolderId = folderId;
-    }
-
-    public synchronized void setSentFolderId(@Nullable Long folderId, SpecialFolderSelection selection) {
-        sentFolderId = folderId;
-        sentFolderSelection = selection;
-    }
-
-    public synchronized boolean hasSentFolder() {
-        return sentFolderId != null;
-    }
-
-    public synchronized String getImportedTrashFolder() {
-        return importedTrashFolder;
-    }
-
-    public synchronized void setImportedTrashFolder(String folderServerId) {
-        importedTrashFolder = folderServerId;
-    }
-
-    @Nullable
-    public synchronized Long getTrashFolderId() {
-        return trashFolderId;
-    }
-
-    public synchronized void setTrashFolderId(@Nullable Long folderId) {
-        trashFolderId = folderId;
-    }
-
-    public synchronized void setTrashFolderId(@Nullable Long folderId, SpecialFolderSelection selection) {
-        trashFolderId = folderId;
-        trashFolderSelection = selection;
-    }
-
-    public synchronized boolean hasTrashFolder() {
-        return trashFolderId != null;
-    }
-
-    public synchronized String getImportedArchiveFolder() {
-        return importedArchiveFolder;
-    }
-
-    public synchronized void setImportedArchiveFolder(String archiveFolder) {
-        this.importedArchiveFolder = archiveFolder;
-    }
-
-    @Nullable
-    public synchronized Long getArchiveFolderId() {
-        return archiveFolderId;
-    }
-
-    public synchronized void setArchiveFolderId(@Nullable Long folderId) {
-        archiveFolderId = folderId;
-    }
-
-    public synchronized void setArchiveFolderId(@Nullable Long folderId, SpecialFolderSelection selection) {
-        this.archiveFolderId = folderId;
-        archiveFolderSelection = selection;
-    }
-
-    public synchronized boolean hasArchiveFolder() {
-        return archiveFolderId != null;
-    }
-
-    public synchronized String getImportedSpamFolder() {
-        return importedSpamFolder;
-    }
-
-    public synchronized void setImportedSpamFolder(String folderServerId) {
-        importedSpamFolder = folderServerId;
-    }
-
-    @Nullable
-    public synchronized Long getSpamFolderId() {
-        return spamFolderId;
-    }
-
-    public synchronized void setSpamFolderId(@Nullable Long folderId) {
-        spamFolderId = folderId;
-    }
-
-    public synchronized void setSpamFolderId(@Nullable Long folderId, SpecialFolderSelection selection) {
-        spamFolderId = folderId;
-        spamFolderSelection = selection;
-    }
-
-    public synchronized boolean hasSpamFolder() {
-        return spamFolderId != null;
-    }
-
-    @NotNull
-    public SpecialFolderSelection getDraftsFolderSelection() {
-        return draftsFolderSelection;
-    }
-
-    @NotNull
-    public synchronized SpecialFolderSelection getSentFolderSelection() {
-        return sentFolderSelection;
-    }
-
-    @NotNull
-    public synchronized SpecialFolderSelection getTrashFolderSelection() {
-        return trashFolderSelection;
-    }
-
-    @NotNull
-    public synchronized SpecialFolderSelection getArchiveFolderSelection() {
-        return archiveFolderSelection;
-    }
-
-    @NotNull
-    public synchronized SpecialFolderSelection getSpamFolderSelection() {
-        return spamFolderSelection;
-    }
-
-    @Nullable
-    public synchronized Long getOutboxFolderId() {
-        return outboxFolderId;
-    }
-
-    public synchronized void setOutboxFolderId(@Nullable Long folderId) {
-        outboxFolderId = folderId;
-    }
-
-    public synchronized String getImportedAutoExpandFolder() {
-        return importedAutoExpandFolder;
-    }
-
-    public synchronized void setImportedAutoExpandFolder(String name) {
-        importedAutoExpandFolder = name;
-    }
-
-    @Nullable
-    public synchronized Long getAutoExpandFolderId() {
-        return autoExpandFolderId;
-    }
-
-    public synchronized void setAutoExpandFolderId(@Nullable Long folderId) {
-        autoExpandFolderId = folderId;
-    }
-
-    public synchronized int getAccountNumber() {
-        return accountNumber;
-    }
-
-    public synchronized void setAccountNumber(int accountNumber) {
-        this.accountNumber = accountNumber;
-    }
-
-    public synchronized FolderMode getFolderDisplayMode() {
-        return folderDisplayMode;
-    }
-
-    public synchronized boolean setFolderDisplayMode(FolderMode displayMode) {
-        FolderMode oldDisplayMode = folderDisplayMode;
-        folderDisplayMode = displayMode;
-        return oldDisplayMode != displayMode;
-    }
-
-    public synchronized FolderMode getFolderSyncMode() {
-        return folderSyncMode;
-    }
-
-    public synchronized boolean setFolderSyncMode(FolderMode syncMode) {
-        FolderMode oldSyncMode = folderSyncMode;
-        folderSyncMode = syncMode;
-
-        if (syncMode == FolderMode.NONE && oldSyncMode != FolderMode.NONE) {
-            return true;
-        }
-        return syncMode != FolderMode.NONE && oldSyncMode == FolderMode.NONE;
-    }
-
-    public synchronized FolderMode getFolderPushMode() {
-        return folderPushMode;
-    }
-
-    public synchronized void setFolderPushMode(FolderMode pushMode) {
-        folderPushMode = pushMode;
-    }
-
-    public synchronized boolean isNotifySync() {
-        return notifySync;
-    }
-
-    public synchronized void setNotifySync(boolean notifySync) {
-        this.notifySync = notifySync;
-    }
-
-    public synchronized int getMessagesNotificationChannelVersion() {
-        return messagesNotificationChannelVersion;
-    }
-
-    public synchronized void setMessagesNotificationChannelVersion(int notificationChannelVersion) {
-        messagesNotificationChannelVersion = notificationChannelVersion;
-    }
-
-    public synchronized void incrementMessagesNotificationChannelVersion() {
-        messagesNotificationChannelVersion++;
-    }
-
-    public synchronized SortType getSortType() {
-        return sortType;
-    }
-
-    public synchronized void setSortType(SortType sortType) {
-        this.sortType = sortType;
-    }
-
-    public synchronized boolean isSortAscending(SortType sortType) {
-        if (sortAscending.get(sortType) == null) {
-            sortAscending.put(sortType, sortType.isDefaultAscending());
-        }
-        return sortAscending.get(sortType);
-    }
-
-    public synchronized void setSortAscending(SortType sortType, boolean sortAscending) {
-        this.sortAscending.put(sortType, sortAscending);
-    }
-
-    public synchronized ShowPictures getShowPictures() {
-        return showPictures;
-    }
-
-    public synchronized void setShowPictures(ShowPictures showPictures) {
-        this.showPictures = showPictures;
-    }
-
-    public synchronized FolderMode getFolderTargetMode() {
-        return folderTargetMode;
-    }
-
-    public synchronized void setFolderTargetMode(FolderMode folderTargetMode) {
-        this.folderTargetMode = folderTargetMode;
-    }
-
-    public synchronized boolean isSignatureBeforeQuotedText() {
-        return isSignatureBeforeQuotedText;
-    }
-
-    public synchronized void setSignatureBeforeQuotedText(boolean mIsSignatureBeforeQuotedText) {
-        this.isSignatureBeforeQuotedText = mIsSignatureBeforeQuotedText;
-    }
-
-    public synchronized boolean isNotifySelfNewMail() {
-        return notifySelfNewMail;
-    }
-
-    public synchronized void setNotifySelfNewMail(boolean notifySelfNewMail) {
-        this.notifySelfNewMail = notifySelfNewMail;
-    }
-
-    public synchronized boolean isNotifyContactsMailOnly() {
-        return notifyContactsMailOnly;
-    }
-
-    public synchronized void setNotifyContactsMailOnly(boolean notifyContactsMailOnly) {
-        this.notifyContactsMailOnly = notifyContactsMailOnly;
-    }
-
-    public synchronized boolean isIgnoreChatMessages() {
-        return ignoreChatMessages;
-    }
-
-    public synchronized void setIgnoreChatMessages(boolean ignoreChatMessages) {
-        this.ignoreChatMessages = ignoreChatMessages;
-    }
-
-    public synchronized Expunge getExpungePolicy() {
-        return expungePolicy;
-    }
-
-    public synchronized void setExpungePolicy(Expunge expungePolicy) {
-        this.expungePolicy = expungePolicy;
-    }
-
-    public synchronized int getMaxPushFolders() {
-        return maxPushFolders;
-    }
-
-    public synchronized boolean setMaxPushFolders(int maxPushFolders) {
-        int oldMaxPushFolders = this.maxPushFolders;
-        this.maxPushFolders = maxPushFolders;
-        return oldMaxPushFolders != maxPushFolders;
-    }
-
-    @NonNull
-    @Override
-    public synchronized String toString() {
-        if (K9.isSensitiveDebugLoggingEnabled()) {
-            return getDisplayName();
-        } else {
-            return accountUuid;
-        }
-    }
-
-    public synchronized void setCompression(NetworkType networkType, boolean useCompression) {
-        compressionMap.put(networkType, useCompression);
-    }
-
-    public synchronized boolean useCompression(NetworkType networkType) {
-        Boolean useCompression = compressionMap.get(networkType);
-        if (useCompression == null) {
-            return true;
-        }
-
-        return useCompression;
-    }
-
-    public Map<NetworkType, Boolean> getCompressionMap() {
-        return Collections.unmodifiableMap(compressionMap);
-    }
-
-    @Override
-    public boolean equals(Object o) {
-        if (o instanceof Account) {
-            return ((Account)o).accountUuid.equals(accountUuid);
-        }
-        return super.equals(o);
-    }
-
-    @Override
-    public int hashCode() {
-        return accountUuid.hashCode();
-    }
-
-    public synchronized List<Identity> getIdentities() {
-        return identities;
-    }
-
-    public synchronized void setIdentities(List<Identity> newIdentities) {
-        identities = new ArrayList<>(newIdentities);
-    }
-
-    public synchronized Identity getIdentity(int i) {
-        if (i < identities.size()) {
-            return identities.get(i);
-        }
-        throw new IllegalArgumentException("Identity with index " + i + " not found");
-    }
-
-    public boolean isAnIdentity(Address[] addrs) {
-        if (addrs == null) {
-            return false;
-        }
-        for (Address addr : addrs) {
-            if (findIdentity(addr) != null) {
-                return true;
-            }
-        }
-
-        return false;
-    }
-
-    public boolean isAnIdentity(Address addr) {
-        return findIdentity(addr) != null;
-    }
-
-    public synchronized Identity findIdentity(Address addr) {
-        for (Identity identity : identities) {
-            String email = identity.getEmail();
-            if (email != null && email.equalsIgnoreCase(addr.getAddress())) {
-                return identity;
-            }
-        }
-        return null;
-    }
-
-    public synchronized Searchable getSearchableFolders() {
-        return searchableFolders;
-    }
-
-    public synchronized void setSearchableFolders(Searchable searchableFolders) {
-        this.searchableFolders = searchableFolders;
-    }
-
-    public synchronized int getIdleRefreshMinutes() {
-        return idleRefreshMinutes;
-    }
-
-    public synchronized void setIdleRefreshMinutes(int idleRefreshMinutes) {
-        this.idleRefreshMinutes = idleRefreshMinutes;
-    }
-
-    public synchronized boolean isSubscribedFoldersOnly() {
-        return subscribedFoldersOnly;
-    }
-
-    public synchronized void setSubscribedFoldersOnly(boolean subscribedFoldersOnly) {
-        this.subscribedFoldersOnly = subscribedFoldersOnly;
-    }
-
-    public synchronized int getMaximumPolledMessageAge() {
-        return maximumPolledMessageAge;
-    }
-
-    public synchronized void setMaximumPolledMessageAge(int maximumPolledMessageAge) {
-        this.maximumPolledMessageAge = maximumPolledMessageAge;
-    }
-
-    public synchronized int getMaximumAutoDownloadMessageSize() {
-        return maximumAutoDownloadMessageSize;
-    }
-
-    public synchronized void setMaximumAutoDownloadMessageSize(int maximumAutoDownloadMessageSize) {
-        this.maximumAutoDownloadMessageSize = maximumAutoDownloadMessageSize;
-    }
-
-    public Date getEarliestPollDate() {
-        int age = getMaximumPolledMessageAge();
-        if (age >= 0) {
-            Calendar now = Calendar.getInstance();
-            now.set(Calendar.HOUR_OF_DAY, 0);
-            now.set(Calendar.MINUTE, 0);
-            now.set(Calendar.SECOND, 0);
-            now.set(Calendar.MILLISECOND, 0);
-            if (age < 28) {
-                now.add(Calendar.DATE, age * -1);
-            } else switch (age) {
-                case 28:
-                    now.add(Calendar.MONTH, -1);
-                    break;
-                case 56:
-                    now.add(Calendar.MONTH, -2);
-                    break;
-                case 84:
-                    now.add(Calendar.MONTH, -3);
-                    break;
-                case 168:
-                    now.add(Calendar.MONTH, -6);
-                    break;
-                case 365:
-                    now.add(Calendar.YEAR, -1);
-                    break;
-                }
-
-            return now.getTime();
-        }
-
-        return null;
-    }
-
-    public MessageFormat getMessageFormat() {
-        return messageFormat;
-    }
-
-    public void setMessageFormat(MessageFormat messageFormat) {
-        this.messageFormat = messageFormat;
-    }
-
-    public synchronized boolean isMessageFormatAuto() {
-        return messageFormatAuto;
-    }
-
-    public synchronized void setMessageFormatAuto(boolean messageFormatAuto) {
-        this.messageFormatAuto = messageFormatAuto;
-    }
-
-    public synchronized boolean isMessageReadReceipt() {
-        return messageReadReceipt;
-    }
-
-    public synchronized void setMessageReadReceipt(boolean messageReadReceipt) {
-        this.messageReadReceipt = messageReadReceipt;
-    }
-
-    public QuoteStyle getQuoteStyle() {
-        return quoteStyle;
-    }
-
-    public void setQuoteStyle(QuoteStyle quoteStyle) {
-        this.quoteStyle = quoteStyle;
-    }
-
-    public synchronized String getQuotePrefix() {
-        return quotePrefix;
-    }
-
-    public synchronized void setQuotePrefix(String quotePrefix) {
-        this.quotePrefix = quotePrefix;
-    }
-
-    public synchronized boolean isDefaultQuotedTextShown() {
-        return defaultQuotedTextShown;
-    }
-
-    public synchronized void setDefaultQuotedTextShown(boolean shown) {
-        defaultQuotedTextShown = shown;
-    }
-
-    public synchronized boolean isReplyAfterQuote() {
-        return replyAfterQuote;
-    }
-
-    public synchronized void setReplyAfterQuote(boolean replyAfterQuote) {
-        this.replyAfterQuote = replyAfterQuote;
-    }
-
-    public synchronized boolean isStripSignature() {
-        return stripSignature;
-    }
-
-    public synchronized void setStripSignature(boolean stripSignature) {
-        this.stripSignature = stripSignature;
-    }
-
-    public boolean isOpenPgpProviderConfigured() {
-        return !TextUtils.isEmpty(openPgpProvider);
-    }
-
-    @Nullable
-    public String getOpenPgpProvider() {
-        if (TextUtils.isEmpty(openPgpProvider)) {
-            return null;
-        }
-        return openPgpProvider;
-    }
-
-    public void setOpenPgpProvider(String openPgpProvider) {
-        this.openPgpProvider = openPgpProvider;
-    }
-
-    public long getOpenPgpKey() {
-        return openPgpKey;
-    }
-
-    public void setOpenPgpKey(long keyId) {
-        openPgpKey = keyId;
-    }
-
-    public boolean hasOpenPgpKey() {
-        return openPgpKey != NO_OPENPGP_KEY;
-    }
-
-    public boolean getAutocryptPreferEncryptMutual() {
-        return autocryptPreferEncryptMutual;
-    }
-
-    public void setAutocryptPreferEncryptMutual(boolean autocryptPreferEncryptMutual) {
-        this.autocryptPreferEncryptMutual = autocryptPreferEncryptMutual;
-    }
-
-    public boolean isOpenPgpHideSignOnly() {
-        return openPgpHideSignOnly;
-    }
-
-    public void setOpenPgpHideSignOnly(boolean openPgpHideSignOnly) {
-        this.openPgpHideSignOnly = openPgpHideSignOnly;
-    }
-
-    public boolean isOpenPgpEncryptSubject() {
-        return openPgpEncryptSubject;
-    }
-
-    public void setOpenPgpEncryptSubject(boolean openPgpEncryptSubject) {
-        this.openPgpEncryptSubject = openPgpEncryptSubject;
-    }
-
-    public boolean isOpenPgpEncryptAllDrafts() {
-        return openPgpEncryptAllDrafts;
-    }
-
-    public void setOpenPgpEncryptAllDrafts(boolean openPgpEncryptAllDrafts) {
-        this.openPgpEncryptAllDrafts = openPgpEncryptAllDrafts;
-    }
-
-    public int getRemoteSearchNumResults() {
-        return remoteSearchNumResults;
-    }
-
-    public void setRemoteSearchNumResults(int val) {
-        remoteSearchNumResults = (val >= 0 ? val : 0);
-    }
-
-    public boolean isUploadSentMessages() {
-        return uploadSentMessages;
-    }
-
-    public void setUploadSentMessages(boolean uploadSentMessages) {
-        this.uploadSentMessages = uploadSentMessages;
-    }
-
-    public String getLegacyInboxFolder() {
-        return legacyInboxFolder;
-    }
-
-    void setLegacyInboxFolder(String name) {
-        this.legacyInboxFolder = name;
-    }
-
-    @Nullable
-    public synchronized Long getInboxFolderId() {
-        return inboxFolderId;
-    }
-
-    public synchronized void setInboxFolderId(@Nullable Long folderId) {
-        inboxFolderId = folderId;
-    }
-
-    public synchronized boolean isSyncRemoteDeletions() {
-        return syncRemoteDeletions;
-    }
-
-    public synchronized void setSyncRemoteDeletions(boolean syncRemoteDeletions) {
-        this.syncRemoteDeletions = syncRemoteDeletions;
-    }
-
-    public synchronized Long getLastSelectedFolderId() {
-        return lastSelectedFolderId;
-    }
-
-    public synchronized void setLastSelectedFolderId(long folderId) {
-        lastSelectedFolderId = folderId;
-    }
-
-    public synchronized NotificationSetting getNotificationSetting() {
-        return notificationSetting;
-    }
-
-    public synchronized boolean isMarkMessageAsReadOnView() {
-        return markMessageAsReadOnView;
-    }
-
-    public synchronized void setMarkMessageAsReadOnView(boolean value) {
-        markMessageAsReadOnView = value;
-    }
-
-    public synchronized boolean isMarkMessageAsReadOnDelete() {
-        return markMessageAsReadOnDelete;
-    }
-
-    public synchronized void setMarkMessageAsReadOnDelete(boolean value) {
-        markMessageAsReadOnDelete = value;
-    }
-
-    public synchronized boolean isAlwaysShowCcBcc() {
-        return alwaysShowCcBcc;
-    }
-
-    public synchronized void setAlwaysShowCcBcc(boolean show) {
-        alwaysShowCcBcc = show;
-    }
-    public boolean isRemoteSearchFullText() {
-        return false;   // Temporarily disabled
-        //return remoteSearchFullText;
-    }
-
-    public void setRemoteSearchFullText(boolean val) {
-        remoteSearchFullText = val;
-    }
-
-    public synchronized long getLastSyncTime() {
-        return lastSyncTime;
-    }
-
-    public synchronized void setLastSyncTime(long lastSyncTime) {
-        this.lastSyncTime = lastSyncTime;
-    }
-
-    public synchronized long getLastFolderListRefreshTime() {
-        return lastFolderListRefreshTime;
-    }
-
-    public synchronized void setLastFolderListRefreshTime(long lastFolderListRefreshTime) {
-        this.lastFolderListRefreshTime = lastFolderListRefreshTime;
-    }
-
-    boolean isChangedVisibleLimits() {
-        return changedVisibleLimits;
-    }
-
-    void resetChangeMarkers() {
-        changedVisibleLimits = false;
-    }
-
-    public synchronized boolean isFinishedSetup() {
-        return isFinishedSetup;
-    }
-
-    public void markSetupFinished() {
-        isFinishedSetup = true;
-    }
-}
diff --git a/app/core/src/main/java/com/fsck/k9/Account.kt b/app/core/src/main/java/com/fsck/k9/Account.kt
new file mode 100644
index 000000000..b32e628e7
--- /dev/null
+++ b/app/core/src/main/java/com/fsck/k9/Account.kt
@@ -0,0 +1,703 @@
+package com.fsck.k9
+
+import com.fsck.k9.backend.api.SyncConfig.ExpungePolicy
+import com.fsck.k9.mail.Address
+import com.fsck.k9.mail.NetworkType
+import com.fsck.k9.mail.ServerSettings
+import java.util.Calendar
+import java.util.Date
+import java.util.concurrent.ConcurrentHashMap
+
+/**
+ * Account stores all of the settings for a single account defined by the user. Each account is defined by a UUID.
+ */
+class Account(override val uuid: String) : BaseAccount {
+    @get:Synchronized
+    @set:Synchronized
+    var deletePolicy = DeletePolicy.NEVER
+
+    @get:Synchronized
+    @set:Synchronized
+    private var internalIncomingServerSettings: ServerSettings? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    private var internalOutgoingServerSettings: ServerSettings? = null
+
+    var incomingServerSettings: ServerSettings
+        get() = internalIncomingServerSettings ?: error("Incoming server settings not set yet")
+        set(value) {
+            internalIncomingServerSettings = value
+        }
+
+    var outgoingServerSettings: ServerSettings
+        get() = internalOutgoingServerSettings ?: error("Outgoing server settings not set yet")
+        set(value) {
+            internalOutgoingServerSettings = value
+        }
+
+    /**
+     * Storage provider ID, used to locate and manage the underlying DB/file storage.
+     */
+    @get:Synchronized
+    @set:Synchronized
+    var localStorageProviderId: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    override var name: String? = null
+        set(value) {
+            field = value?.takeIf { it.isNotEmpty() }
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var alwaysBcc: String? = null
+
+    /**
+     * -1 for never.
+     */
+    @get:Synchronized
+    @set:Synchronized
+    var automaticCheckIntervalMinutes = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var displayCount = 0
+        set(value) {
+            if (field != value) {
+                field = value.takeIf { it != -1 } ?: K9.DEFAULT_VISIBLE_LIMIT
+                isChangedVisibleLimits = true
+            }
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var chipColor = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var isNotifyNewMail = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var folderNotifyNewMailMode = FolderMode.ALL
+
+    @get:Synchronized
+    @set:Synchronized
+    var isNotifySelfNewMail = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isNotifyContactsMailOnly = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isIgnoreChatMessages = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var legacyInboxFolder: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var importedDraftsFolder: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var importedSentFolder: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var importedTrashFolder: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var importedArchiveFolder: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var importedSpamFolder: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var inboxFolderId: Long? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var outboxFolderId: Long? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var draftsFolderId: Long? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var sentFolderId: Long? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var trashFolderId: Long? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var archiveFolderId: Long? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var spamFolderId: Long? = null
+
+    @get:Synchronized
+    var draftsFolderSelection = SpecialFolderSelection.AUTOMATIC
+        private set
+
+    @get:Synchronized
+    var sentFolderSelection = SpecialFolderSelection.AUTOMATIC
+        private set
+
+    @get:Synchronized
+    var trashFolderSelection = SpecialFolderSelection.AUTOMATIC
+        private set
+
+    @get:Synchronized
+    var archiveFolderSelection = SpecialFolderSelection.AUTOMATIC
+        private set
+
+    @get:Synchronized
+    var spamFolderSelection = SpecialFolderSelection.AUTOMATIC
+        private set
+
+    @get:Synchronized
+    @set:Synchronized
+    var importedAutoExpandFolder: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var autoExpandFolderId: Long? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var folderDisplayMode = FolderMode.NOT_SECOND_CLASS
+
+    @get:Synchronized
+    @set:Synchronized
+    var folderSyncMode = FolderMode.FIRST_CLASS
+
+    @get:Synchronized
+    @set:Synchronized
+    var folderPushMode = FolderMode.NONE
+
+    @get:Synchronized
+    @set:Synchronized
+    var folderTargetMode = FolderMode.NOT_SECOND_CLASS
+
+    @get:Synchronized
+    @set:Synchronized
+    var accountNumber = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var isNotifySync = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var sortType: SortType = SortType.SORT_DATE
+
+    private val sortAscending: MutableMap<SortType, Boolean> = mutableMapOf()
+
+    @get:Synchronized
+    @set:Synchronized
+    var showPictures = ShowPictures.NEVER
+
+    @get:Synchronized
+    @set:Synchronized
+    var isSignatureBeforeQuotedText = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var expungePolicy = Expunge.EXPUNGE_IMMEDIATELY
+
+    @get:Synchronized
+    @set:Synchronized
+    var maxPushFolders = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var idleRefreshMinutes = 0
+
+    private val compressionMap: MutableMap<NetworkType, Boolean> = ConcurrentHashMap()
+
+    @get:Synchronized
+    @set:Synchronized
+    var searchableFolders = Searchable.ALL
+
+    @get:Synchronized
+    @set:Synchronized
+    var isSubscribedFoldersOnly = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var maximumPolledMessageAge = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var maximumAutoDownloadMessageSize = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var messageFormat = MessageFormat.HTML
+
+    @get:Synchronized
+    @set:Synchronized
+    var isMessageFormatAuto = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isMessageReadReceipt = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var quoteStyle = QuoteStyle.PREFIX
+
+    @get:Synchronized
+    @set:Synchronized
+    var quotePrefix: String? = null
+
+    @get:Synchronized
+    @set:Synchronized
+    var isDefaultQuotedTextShown = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isReplyAfterQuote = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isStripSignature = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isSyncRemoteDeletions = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var openPgpProvider: String? = null
+        set(value) {
+            field = value?.takeIf { it.isNotEmpty() }
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var openPgpKey: Long = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var autocryptPreferEncryptMutual = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isOpenPgpHideSignOnly = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isOpenPgpEncryptSubject = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isOpenPgpEncryptAllDrafts = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isMarkMessageAsReadOnView = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isMarkMessageAsReadOnDelete = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var isAlwaysShowCcBcc = false
+
+    // Temporarily disabled
+    @get:Synchronized
+    @set:Synchronized
+    var isRemoteSearchFullText = false
+        get() = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var remoteSearchNumResults = 0
+        set(value) {
+            field = value.coerceAtLeast(0)
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var isUploadSentMessages = false
+
+    @get:Synchronized
+    @set:Synchronized
+    var lastSyncTime: Long = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var lastFolderListRefreshTime: Long = 0
+
+    @get:Synchronized
+    var isFinishedSetup = false
+        private set
+
+    @get:Synchronized
+    @set:Synchronized
+    var messagesNotificationChannelVersion = 0
+
+    @get:Synchronized
+    @set:Synchronized
+    var isChangedVisibleLimits = false
+        private set
+
+    /**
+     * Database ID of the folder that was last selected for a copy or move operation.
+     *
+     * Note: For now this value isn't persisted. So it will be reset when K-9 Mail is restarted.
+     */
+    @get:Synchronized
+    var lastSelectedFolderId: Long? = null
+        private set
+
+    @get:Synchronized
+    @set:Synchronized
+    var identities: MutableList<Identity> = mutableListOf()
+        set(value) {
+            field = value.toMutableList()
+        }
+
+    @get:Synchronized
+    var notificationSettings = NotificationSettings()
+        private set
+
+    val displayName: String
+        get() = name ?: email
+
+    @get:Synchronized
+    @set:Synchronized
+    override var email: String
+        get() = identities[0].email!!
+        set(email) {
+            val newIdentity = identities[0].withEmail(email)
+            identities[0] = newIdentity
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var senderName: String?
+        get() = identities[0].name
+        set(name) {
+            val newIdentity = identities[0].withName(name)
+            identities[0] = newIdentity
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var signatureUse: Boolean
+        get() = identities[0].signatureUse
+        set(signatureUse) {
+            val newIdentity = identities[0].withSignatureUse(signatureUse)
+            identities[0] = newIdentity
+        }
+
+    @get:Synchronized
+    @set:Synchronized
+    var signature: String?
+        get() = identities[0].signature
+        set(signature) {
+            val newIdentity = identities[0].withSignature(signature)
+            identities[0] = newIdentity
+        }
+
+    /**
+     * @param automaticCheckIntervalMinutes or -1 for never.
+     */
+    @Synchronized
+    fun updateAutomaticCheckIntervalMinutes(automaticCheckIntervalMinutes: Int): Boolean {
+        val oldInterval = this.automaticCheckIntervalMinutes
+        this.automaticCheckIntervalMinutes = automaticCheckIntervalMinutes
+
+        return oldInterval != automaticCheckIntervalMinutes
+    }
+
+    @Synchronized
+    fun setDraftsFolderId(folderId: Long?, selection: SpecialFolderSelection) {
+        draftsFolderId = folderId
+        draftsFolderSelection = selection
+    }
+
+    @Synchronized
+    fun hasDraftsFolder(): Boolean {
+        return draftsFolderId != null
+    }
+
+    @Synchronized
+    fun setSentFolderId(folderId: Long?, selection: SpecialFolderSelection) {
+        sentFolderId = folderId
+        sentFolderSelection = selection
+    }
+
+    @Synchronized
+    fun hasSentFolder(): Boolean {
+        return sentFolderId != null
+    }
+
+    @Synchronized
+    fun setTrashFolderId(folderId: Long?, selection: SpecialFolderSelection) {
+        trashFolderId = folderId
+        trashFolderSelection = selection
+    }
+
+    @Synchronized
+    fun hasTrashFolder(): Boolean {
+        return trashFolderId != null
+    }
+
+    @Synchronized
+    fun setArchiveFolderId(folderId: Long?, selection: SpecialFolderSelection) {
+        archiveFolderId = folderId
+        archiveFolderSelection = selection
+    }
+
+    @Synchronized
+    fun hasArchiveFolder(): Boolean {
+        return archiveFolderId != null
+    }
+
+    @Synchronized
+    fun setSpamFolderId(folderId: Long?, selection: SpecialFolderSelection) {
+        spamFolderId = folderId
+        spamFolderSelection = selection
+    }
+
+    @Synchronized
+    fun hasSpamFolder(): Boolean {
+        return spamFolderId != null
+    }
+
+    @Synchronized
+    fun updateFolderSyncMode(syncMode: FolderMode): Boolean {
+        val oldSyncMode = folderSyncMode
+        folderSyncMode = syncMode
+
+        return (oldSyncMode == FolderMode.NONE && syncMode != FolderMode.NONE) ||
+            (oldSyncMode != FolderMode.NONE && syncMode == FolderMode.NONE)
+    }
+
+    @Synchronized
+    fun incrementMessagesNotificationChannelVersion() {
+        messagesNotificationChannelVersion++
+    }
+
+    @Synchronized
+    fun isSortAscending(sortType: SortType): Boolean {
+        return sortAscending.getOrPut(sortType) { sortType.isDefaultAscending }
+    }
+
+    @Synchronized
+    fun setSortAscending(sortType: SortType, sortAscending: Boolean) {
+        this.sortAscending[sortType] = sortAscending
+    }
+
+    @Synchronized
+    fun setCompression(networkType: NetworkType, useCompression: Boolean) {
+        compressionMap[networkType] = useCompression
+    }
+
+    @Synchronized
+    fun useCompression(networkType: NetworkType): Boolean {
+        return compressionMap[networkType] ?: return true
+    }
+
+    fun getCompressionMap(): Map<NetworkType, Boolean> {
+        return compressionMap.toMap()
+    }
+
+    @Synchronized
+    fun replaceIdentities(identities: List<Identity>) {
+        this.identities = identities.toMutableList()
+    }
+
+    @Synchronized
+    fun getIdentity(index: Int): Identity {
+        if (index !in identities.indices) error("Identity with index $index not found")
+
+        return identities[index]
+    }
+
+    fun isAnIdentity(addresses: Array<Address>?): Boolean {
+        if (addresses == null) return false
+
+        return addresses.any { address -> isAnIdentity(address) }
+    }
+
+    fun isAnIdentity(address: Address): Boolean {
+        return findIdentity(address) != null
+    }
+
+    @Synchronized
+    fun findIdentity(address: Address): Identity? {
+        return identities.find { identity ->
+            identity.email.equals(address.address, ignoreCase = true)
+        }
+    }
+
+    val earliestPollDate: Date?
+        get() {
+            val age = maximumPolledMessageAge.takeIf { it >= 0 } ?: return null
+
+            val now = Calendar.getInstance()
+            now[Calendar.HOUR_OF_DAY] = 0
+            now[Calendar.MINUTE] = 0
+            now[Calendar.SECOND] = 0
+            now[Calendar.MILLISECOND] = 0
+
+            if (age < 28) {
+                now.add(Calendar.DATE, age * -1)
+            } else when (age) {
+                28 -> now.add(Calendar.MONTH, -1)
+                56 -> now.add(Calendar.MONTH, -2)
+                84 -> now.add(Calendar.MONTH, -3)
+                168 -> now.add(Calendar.MONTH, -6)
+                365 -> now.add(Calendar.YEAR, -1)
+            }
+
+            return now.time
+        }
+
+    val isOpenPgpProviderConfigured: Boolean
+        get() = openPgpProvider != null
+
+    @Synchronized
+    fun hasOpenPgpKey(): Boolean {
+        return openPgpKey != NO_OPENPGP_KEY
+    }
+
+    @Synchronized
+    fun setLastSelectedFolderId(folderId: Long) {
+        lastSelectedFolderId = folderId
+    }
+
+    @Synchronized
+    fun resetChangeMarkers() {
+        isChangedVisibleLimits = false
+    }
+
+    @Synchronized
+    fun markSetupFinished() {
+        isFinishedSetup = true
+    }
+
+    @Synchronized
+    fun updateNotificationSettings(block: (oldNotificationSettings: NotificationSettings) -> NotificationSettings) {
+        notificationSettings = block(notificationSettings)
+    }
+
+    override fun toString(): String {
+        return if (K9.isSensitiveDebugLoggingEnabled) displayName else uuid
+    }
+
+    override fun equals(other: Any?): Boolean {
+        return if (other is Account) {
+            other.uuid == uuid
+        } else {
+            super.equals(other)
+        }
+    }
+
+    override fun hashCode(): Int {
+        return uuid.hashCode()
+    }
+
+    enum class FolderMode {
+        NONE,
+        ALL,
+        FIRST_CLASS,
+        FIRST_AND_SECOND_CLASS,
+        NOT_SECOND_CLASS
+    }
+
+    enum class SpecialFolderSelection {
+        AUTOMATIC,
+        MANUAL
+    }
+
+    enum class ShowPictures {
+        NEVER,
+        ALWAYS,
+        ONLY_FROM_CONTACTS
+    }
+
+    enum class Searchable {
+        ALL,
+        DISPLAYABLE,
+        NONE
+    }
+
+    enum class QuoteStyle {
+        PREFIX,
+        HEADER
+    }
+
+    enum class MessageFormat {
+        TEXT,
+        HTML,
+        AUTO
+    }
+
+    enum class Expunge {
+        EXPUNGE_IMMEDIATELY,
+        EXPUNGE_MANUALLY,
+        EXPUNGE_ON_POLL;
+
+        fun toBackendExpungePolicy(): ExpungePolicy = when (this) {
+            EXPUNGE_IMMEDIATELY -> ExpungePolicy.IMMEDIATELY
+            EXPUNGE_MANUALLY -> ExpungePolicy.MANUALLY
+            EXPUNGE_ON_POLL -> ExpungePolicy.ON_POLL
+        }
+    }
+
+    enum class DeletePolicy(@JvmField val setting: Int) {
+        NEVER(0),
+        SEVEN_DAYS(1),
+        ON_DELETE(2),
+        MARK_AS_READ(3);
+
+        companion object {
+            fun fromInt(initialSetting: Int): DeletePolicy {
+                return values().find { it.setting == initialSetting } ?: error("DeletePolicy $initialSetting unknown")
+            }
+        }
+    }
+
+    enum class SortType(val isDefaultAscending: Boolean) {
+        SORT_DATE(false),
+        SORT_ARRIVAL(false),
+        SORT_SUBJECT(true),
+        SORT_SENDER(true),
+        SORT_UNREAD(true),
+        SORT_FLAGGED(true),
+        SORT_ATTACHMENT(true);
+    }
+
+    companion object {
+        /**
+         * Fixed name of outbox - not actually displayed.
+         */
+        const val OUTBOX_NAME = "Outbox"
+
+        @JvmField
+        val DEFAULT_SORT_TYPE = SortType.SORT_DATE
+        const val DEFAULT_SORT_ASCENDING = false
+        const val NO_OPENPGP_KEY: Long = 0
+        const val UNASSIGNED_ACCOUNT_NUMBER = -1
+        const val INTERVAL_MINUTES_NEVER = -1
+        const val DEFAULT_SYNC_INTERVAL = 60
+    }
+}
diff --git a/app/core/src/main/java/com/fsck/k9/AccountPreferenceSerializer.kt b/app/core/src/main/java/com/fsck/k9/AccountPreferenceSerializer.kt
index 13d81b3de..39a79c2cb 100644
--- a/app/core/src/main/java/com/fsck/k9/AccountPreferenceSerializer.kt
+++ b/app/core/src/main/java/com/fsck/k9/AccountPreferenceSerializer.kt
@@ -1,19 +1,19 @@
 package com.fsck.k9
 
-import com.fsck.k9.Account.DEFAULT_SORT_ASCENDING
-import com.fsck.k9.Account.DEFAULT_SORT_TYPE
-import com.fsck.k9.Account.DEFAULT_SYNC_INTERVAL
+import com.fsck.k9.Account.Companion.DEFAULT_SORT_ASCENDING
+import com.fsck.k9.Account.Companion.DEFAULT_SORT_TYPE
+import com.fsck.k9.Account.Companion.DEFAULT_SYNC_INTERVAL
+import com.fsck.k9.Account.Companion.NO_OPENPGP_KEY
+import com.fsck.k9.Account.Companion.UNASSIGNED_ACCOUNT_NUMBER
 import com.fsck.k9.Account.DeletePolicy
 import com.fsck.k9.Account.Expunge
 import com.fsck.k9.Account.FolderMode
 import com.fsck.k9.Account.MessageFormat
-import com.fsck.k9.Account.NO_OPENPGP_KEY
 import com.fsck.k9.Account.QuoteStyle
 import com.fsck.k9.Account.Searchable
 import com.fsck.k9.Account.ShowPictures
 import com.fsck.k9.Account.SortType
 import com.fsck.k9.Account.SpecialFolderSelection
-import com.fsck.k9.Account.UNASSIGNED_ACCOUNT_NUMBER
 import com.fsck.k9.helper.Utility
 import com.fsck.k9.mail.NetworkType
 import com.fsck.k9.mailstore.StorageManager
@@ -137,16 +137,17 @@ class AccountPreferenceSerializer(
 
             showPictures = getEnumStringPref<ShowPictures>(storage, "$accountUuid.showPicturesEnum", ShowPictures.NEVER)
 
-            notificationSetting.isVibrateEnabled = storage.getBoolean("$accountUuid.vibrate", false)
-            notificationSetting.vibratePattern = storage.getInt("$accountUuid.vibratePattern", 0)
-            notificationSetting.vibrateTimes = storage.getInt("$accountUuid.vibrateTimes", 5)
-            notificationSetting.isRingEnabled = storage.getBoolean("$accountUuid.ring", true)
-            notificationSetting.ringtone = storage.getString(
-                "$accountUuid.ringtone",
-                "content://settings/system/notification_sound"
-            )
-            notificationSetting.setLed(storage.getBoolean("$accountUuid.led", true))
-            notificationSetting.ledColor = storage.getInt("$accountUuid.ledColor", chipColor)
+            updateNotificationSettings {
+                NotificationSettings(
+                    isRingEnabled = storage.getBoolean("$accountUuid.ring", true),
+                    ringtone = storage.getString("$accountUuid.ringtone", DEFAULT_RINGTONE_URI),
+                    isLedEnabled = storage.getBoolean("$accountUuid.led", true),
+                    ledColor = storage.getInt("$accountUuid.ledColor", chipColor),
+                    isVibrateEnabled = storage.getBoolean("$accountUuid.vibrate", false),
+                    vibratePattern = VibratePattern.deserialize(storage.getInt("$accountUuid.vibratePattern", 0)),
+                    vibrateTimes = storage.getInt("$accountUuid.vibrateTimes", 5)
+                )
+            }
 
             folderDisplayMode = getEnumStringPref<FolderMode>(storage, "$accountUuid.folderDisplayMode", FolderMode.NOT_SECOND_CLASS)
 
@@ -159,7 +160,7 @@ class AccountPreferenceSerializer(
             searchableFolders = getEnumStringPref<Searchable>(storage, "$accountUuid.searchableFolders", Searchable.ALL)
 
             isSignatureBeforeQuotedText = storage.getBoolean("$accountUuid.signatureBeforeQuotedText", false)
-            identities = loadIdentities(accountUuid, storage)
+            replaceIdentities(loadIdentities(accountUuid, storage))
 
             openPgpProvider = storage.getString("$accountUuid.openPgpProvider", "")
             openPgpKey = storage.getLong("$accountUuid.cryptoKey", NO_OPENPGP_KEY)
@@ -322,17 +323,18 @@ class AccountPreferenceSerializer(
             editor.putBoolean("$accountUuid.markMessageAsReadOnDelete", isMarkMessageAsReadOnDelete)
             editor.putBoolean("$accountUuid.alwaysShowCcBcc", isAlwaysShowCcBcc)
 
-            editor.putBoolean("$accountUuid.vibrate", notificationSetting.isVibrateEnabled)
-            editor.putInt("$accountUuid.vibratePattern", notificationSetting.vibratePattern)
-            editor.putInt("$accountUuid.vibrateTimes", notificationSetting.vibrateTimes)
-            editor.putBoolean("$accountUuid.ring", notificationSetting.isRingEnabled)
-            editor.putString("$accountUuid.ringtone", notificationSetting.ringtone)
-            editor.putBoolean("$accountUuid.led", notificationSetting.isLedEnabled)
-            editor.putInt("$accountUuid.ledColor", notificationSetting.ledColor)
+            editor.putBoolean("$accountUuid.vibrate", notificationSettings.isVibrateEnabled)
+            editor.putInt("$accountUuid.vibratePattern", notificationSettings.vibratePattern.serialize())
+            editor.putInt("$accountUuid.vibrateTimes", notificationSettings.vibrateTimes)
+            editor.putBoolean("$accountUuid.ring", notificationSettings.isRingEnabled)
+            editor.putString("$accountUuid.ringtone", notificationSettings.ringtone)
+            editor.putBoolean("$accountUuid.led", notificationSettings.isLedEnabled)
+            editor.putInt("$accountUuid.ledColor", notificationSettings.ledColor)
             editor.putLong("$accountUuid.lastSyncTime", lastSyncTime)
             editor.putLong("$accountUuid.lastFolderListRefreshTime", lastFolderListRefreshTime)
             editor.putBoolean("$accountUuid.isFinishedSetup", isFinishedSetup)
 
+            val compressionMap = getCompressionMap()
             for (type in NetworkType.values()) {
                 val useCompression = compressionMap[type]
                 if (useCompression != null) {
@@ -603,13 +605,16 @@ class AccountPreferenceSerializer(
             )
             identities.add(identity)
 
-            with(notificationSetting) {
-                isVibrateEnabled = false
-                vibratePattern = 0
-                vibrateTimes = 5
-                isRingEnabled = true
-                ringtone = "content://settings/system/notification_sound"
-                ledColor = chipColor
+            updateNotificationSettings {
+                NotificationSettings(
+                    isRingEnabled = true,
+                    ringtone = DEFAULT_RINGTONE_URI,
+                    isLedEnabled = false,
+                    ledColor = chipColor,
+                    isVibrateEnabled = false,
+                    vibratePattern = VibratePattern.Default,
+                    vibrateTimes = 5
+                )
             }
 
             resetChangeMarkers()
@@ -639,5 +644,6 @@ class AccountPreferenceSerializer(
         const val DEFAULT_REPLY_AFTER_QUOTE = false
         const val DEFAULT_STRIP_SIGNATURE = true
         const val DEFAULT_REMOTE_SEARCH_NUM_RESULTS = 25
+        const val DEFAULT_RINGTONE_URI = "content://settings/system/notification_sound"
     }
 }
diff --git a/app/core/src/main/java/com/fsck/k9/BaseAccount.java b/app/core/src/main/java/com/fsck/k9/BaseAccount.java
deleted file mode 100644
index 5e62cd1b1..000000000
--- a/app/core/src/main/java/com/fsck/k9/BaseAccount.java
+++ /dev/null
@@ -1,7 +0,0 @@
-package com.fsck.k9;
-
-public interface BaseAccount {
-    String getEmail();
-    String getName();
-    String getUuid();
-}
diff --git a/app/core/src/main/java/com/fsck/k9/BaseAccount.kt b/app/core/src/main/java/com/fsck/k9/BaseAccount.kt
new file mode 100644
index 000000000..330418bad
--- /dev/null
+++ b/app/core/src/main/java/com/fsck/k9/BaseAccount.kt
@@ -0,0 +1,7 @@
+package com.fsck.k9
+
+interface BaseAccount {
+    val uuid: String
+    val name: String?
+    val email: String
+}
diff --git a/app/core/src/main/java/com/fsck/k9/NotificationSetting.java b/app/core/src/main/java/com/fsck/k9/NotificationSetting.java
deleted file mode 100644
index c9d69f249..000000000
--- a/app/core/src/main/java/com/fsck/k9/NotificationSetting.java
+++ /dev/null
@@ -1,138 +0,0 @@
-package com.fsck.k9;
-
-/**
- * Describes how a notification should behave.
- */
-public class NotificationSetting {
-    private boolean ringEnabled;
-    private String ringtoneUri;
-
-    private boolean ledEnabled;
-    private int ledColor;
-
-    private boolean vibrateEnabled;
-
-    private int vibratePattern;
-    private int vibrateTimes;
-
-    /**
-     * Set the ringtone kill switch. Allow to disable ringtone without losing
-     * ringtone selection.
-     *
-     * @param ringEnabled
-     *            <code>true</code> to allow ringtones, <code>false</code>
-     *            otherwise.
-     */
-    public synchronized void setRingEnabled(boolean ringEnabled) {
-        this.ringEnabled = ringEnabled;
-    }
-
-    /**
-     * @return <code>true</code> if ringtone is allowed to play,
-     *         <code>false</code> otherwise.
-     */
-    public synchronized boolean isRingEnabled() {
-        return ringEnabled;
-    }
-
-    public synchronized String getRingtone() {
-        return ringtoneUri;
-    }
-
-    public synchronized void setRingtone(String ringtoneUri) {
-        this.ringtoneUri = ringtoneUri;
-    }
-
-    public synchronized boolean isLedEnabled() {
-        return ledEnabled;
-    }
-
-    public synchronized void setLed(final boolean led) {
-        ledEnabled = led;
-    }
-
-    public synchronized int getLedColor() {
-        return ledColor;
-    }
-
-    public synchronized void setLedColor(int color) {
-        ledColor = color;
-    }
-
-    public synchronized boolean isVibrateEnabled() {
-        return vibrateEnabled;
-    }
-
-    public synchronized void setVibrateEnabled(boolean vibrate) {
-        vibrateEnabled = vibrate;
-    }
-
-    public synchronized int getVibratePattern() {
-        return vibratePattern;
-    }
-
-    public synchronized int getVibrateTimes() {
-        return vibrateTimes;
-    }
-
-    public synchronized void setVibratePattern(int pattern) {
-        vibratePattern = pattern;
-    }
-
-    public synchronized void setVibrateTimes(int times) {
-        vibrateTimes = times;
-    }
-
-
-
-    /*
-     * Fetch a vibration pattern.
-     *
-     * @param vibratePattern Vibration pattern index to use.
-     * @param vibrateTimes Number of times to do the vibration pattern.
-     * @return Pattern multiplied by the number of times requested.
-     */
-
-    public long[] getVibration() {
-        return getVibration(vibratePattern, vibrateTimes);
-    }
-
-    public static long[] getVibration(int pattern, int times) {
-        // These are "off, on" patterns, specified in milliseconds
-        long[] pattern0 = new long[] {300, 200}; // like the default pattern
-        long[] pattern1 = new long[] {100, 200};
-        long[] pattern2 = new long[] {100, 500};
-        long[] pattern3 = new long[] {200, 200};
-        long[] pattern4 = new long[] {200, 500};
-        long[] pattern5 = new long[] {500, 500};
-
-        long[] selectedPattern = pattern0; //default pattern
-
-        switch (pattern) {
-        case 1:
-            selectedPattern = pattern1;
-            break;
-        case 2:
-            selectedPattern = pattern2;
-            break;
-        case 3:
-            selectedPattern = pattern3;
-            break;
-        case 4:
-            selectedPattern = pattern4;
-            break;
-        case 5:
-            selectedPattern = pattern5;
-            break;
-        }
-
-        long[] repeatedPattern = new long[selectedPattern.length * times];
-        for (int n = 0; n < times; n++) {
-            System.arraycopy(selectedPattern, 0, repeatedPattern, n * selectedPattern.length, selectedPattern.length);
-        }
-        // Do not wait before starting the vibration pattern.
-        repeatedPattern[0] = 0;
-        return repeatedPattern;
-    }
-
-}
diff --git a/app/core/src/main/java/com/fsck/k9/NotificationSettings.kt b/app/core/src/main/java/com/fsck/k9/NotificationSettings.kt
new file mode 100644
index 000000000..2f7d29a38
--- /dev/null
+++ b/app/core/src/main/java/com/fsck/k9/NotificationSettings.kt
@@ -0,0 +1,67 @@
+package com.fsck.k9
+
+/**
+ * Describes how a notification should behave.
+ */
+data class NotificationSettings(
+    val isRingEnabled: Boolean = false,
+    val ringtone: String? = null,
+    val isLedEnabled: Boolean = false,
+    val ledColor: Int = 0,
+    val isVibrateEnabled: Boolean = false,
+    val vibratePattern: VibratePattern = VibratePattern.Default,
+    val vibrateTimes: Int = 0
+) {
+    val vibrationPattern: LongArray
+        get() = getVibrationPattern(vibratePattern, vibrateTimes)
+
+    companion object {
+        fun getVibrationPattern(vibratePattern: VibratePattern, times: Int): LongArray {
+            val selectedPattern = vibratePattern.vibrationPattern
+            val repeatedPattern = LongArray(selectedPattern.size * times)
+            for (n in 0 until times) {
+                System.arraycopy(selectedPattern, 0, repeatedPattern, n * selectedPattern.size, selectedPattern.size)
+            }
+
+            // Do not wait before starting the vibration pattern.
+            repeatedPattern[0] = 0
+
+            return repeatedPattern
+        }
+    }
+}
+
+enum class VibratePattern(
+    /**
+     * These are "off, on" patterns, specified in milliseconds.
+     */
+    val vibrationPattern: LongArray
+) {
+    Default(vibrationPattern = longArrayOf(300, 200)),
+    Pattern1(vibrationPattern = longArrayOf(100, 200)),
+    Pattern2(vibrationPattern = longArrayOf(100, 500)),
+    Pattern3(vibrationPattern = longArrayOf(200, 200)),
+    Pattern4(vibrationPattern = longArrayOf(200, 500)),
+    Pattern5(vibrationPattern = longArrayOf(500, 500));
+
+    fun serialize(): Int = when (this) {
+        Default -> 0
+        Pattern1 -> 1
+        Pattern2 -> 2
+        Pattern3 -> 3
+        Pattern4 -> 4
+        Pattern5 -> 5
+    }
+
+    companion object {
+        fun deserialize(value: Int): VibratePattern = when (value) {
+            0 -> Default
+            1 -> Pattern1
+            2 -> Pattern2
+            3 -> Pattern3
+            4 -> Pattern4
+            5 -> Pattern5
+            else -> error("Unknown VibratePattern value: $value")
+        }
+    }
+}
diff --git a/app/core/src/main/java/com/fsck/k9/notification/BaseNotificationDataCreator.kt b/app/core/src/main/java/com/fsck/k9/notification/BaseNotificationDataCreator.kt
index 86f44c861..6a45e8995 100644
--- a/app/core/src/main/java/com/fsck/k9/notification/BaseNotificationDataCreator.kt
+++ b/app/core/src/main/java/com/fsck/k9/notification/BaseNotificationDataCreator.kt
@@ -40,8 +40,8 @@ internal class BaseNotificationDataCreator {
     }
 
     private fun createNotificationAppearance(account: Account): NotificationAppearance {
-        return with(account.notificationSetting) {
-            val vibrationPattern = if (isVibrateEnabled) vibration else null
+        return with(account.notificationSettings) {
+            val vibrationPattern = if (isVibrateEnabled) vibrationPattern else null
             NotificationAppearance(ringtone, vibrationPattern, ledColor)
         }
     }
diff --git a/app/core/src/main/java/com/fsck/k9/notification/NotificationChannelManager.kt b/app/core/src/main/java/com/fsck/k9/notification/NotificationChannelManager.kt
index 0410c7f47..948df9a20 100644
--- a/app/core/src/main/java/com/fsck/k9/notification/NotificationChannelManager.kt
+++ b/app/core/src/main/java/com/fsck/k9/notification/NotificationChannelManager.kt
@@ -6,7 +6,7 @@ import android.app.NotificationManager
 import android.os.Build
 import androidx.annotation.RequiresApi
 import com.fsck.k9.Account
-import com.fsck.k9.NotificationSetting
+import com.fsck.k9.NotificationSettings
 import com.fsck.k9.Preferences
 import java.util.concurrent.Executor
 import timber.log.Timber
@@ -165,7 +165,7 @@ class NotificationChannelManager(
         val oldChannelId = getChannelIdFor(account, ChannelType.MESSAGES)
         val oldNotificationChannel = notificationManager.getNotificationChannel(oldChannelId)
 
-        if (oldNotificationChannel.matches(account.notificationSetting)) {
+        if (oldNotificationChannel.matches(account.notificationSettings)) {
             Timber.v("Not recreating NotificationChannel. The current one already matches the app's settings.")
             return
         }
@@ -183,7 +183,7 @@ class NotificationChannelManager(
             group = account.uuid
 
             copyPropertiesFrom(oldNotificationChannel)
-            copyPropertiesFrom(account.notificationSetting)
+            copyPropertiesFrom(account.notificationSettings)
         }
 
         Timber.v("Recreating NotificationChannel(%s => %s)", oldChannelId, newChannelId)
@@ -191,10 +191,10 @@ class NotificationChannelManager(
     }
 
     @RequiresApi(Build.VERSION_CODES.O)
-    private fun NotificationChannel.matches(notificationSetting: NotificationSetting): Boolean {
-        return lightColor == notificationSetting.ledColor &&
-            shouldVibrate() == notificationSetting.isVibrateEnabled &&
-            vibrationPattern.contentEquals(notificationSetting.vibration)
+    private fun NotificationChannel.matches(notificationSettings: NotificationSettings): Boolean {
+        return lightColor == notificationSettings.ledColor &&
+            shouldVibrate() == notificationSettings.isVibrateEnabled &&
+            vibrationPattern.contentEquals(notificationSettings.vibrationPattern)
     }
 
     @RequiresApi(Build.VERSION_CODES.O)
@@ -211,10 +211,10 @@ class NotificationChannelManager(
     }
 
     @RequiresApi(Build.VERSION_CODES.O)
-    private fun NotificationChannel.copyPropertiesFrom(notificationSetting: NotificationSetting) {
-        lightColor = notificationSetting.ledColor
-        vibrationPattern = notificationSetting.vibration
-        enableVibration(notificationSetting.isVibrateEnabled)
+    private fun NotificationChannel.copyPropertiesFrom(notificationSettings: NotificationSettings) {
+        lightColor = notificationSettings.ledColor
+        vibrationPattern = notificationSettings.vibrationPattern
+        enableVibration(notificationSettings.isVibrateEnabled)
     }
 
     private val Account.messagesNotificationChannelSuffix: String
diff --git a/app/core/src/main/java/com/fsck/k9/notification/SyncNotificationController.kt b/app/core/src/main/java/com/fsck/k9/notification/SyncNotificationController.kt
index e127136c8..ab69e4494 100644
--- a/app/core/src/main/java/com/fsck/k9/notification/SyncNotificationController.kt
+++ b/app/core/src/main/java/com/fsck/k9/notification/SyncNotificationController.kt
@@ -41,7 +41,7 @@ internal class SyncNotificationController(
                 builder = notificationBuilder,
                 ringtone = null,
                 vibrationPattern = null,
-                ledColor = account.notificationSetting.ledColor,
+                ledColor = account.notificationSettings.ledColor,
                 ledSpeed = NotificationHelper.NOTIFICATION_LED_BLINK_FAST,
                 ringAndVibrate = true
             )
@@ -88,7 +88,7 @@ internal class SyncNotificationController(
                 builder = notificationBuilder,
                 ringtone = null,
                 vibrationPattern = null,
-                ledColor = account.notificationSetting.ledColor,
+                ledColor = account.notificationSettings.ledColor,
                 ledSpeed = NotificationHelper.NOTIFICATION_LED_BLINK_FAST,
                 ringAndVibrate = true
             )
@@ -118,7 +118,7 @@ internal class SyncNotificationController(
                 builder = notificationBuilder,
                 ringtone = null,
                 vibrationPattern = null,
-                ledColor = account.notificationSetting.ledColor,
+                ledColor = account.notificationSettings.ledColor,
                 ledSpeed = NotificationHelper.NOTIFICATION_LED_BLINK_FAST,
                 ringAndVibrate = true
             )
diff --git a/app/core/src/main/java/com/fsck/k9/search/SearchAccount.java b/app/core/src/main/java/com/fsck/k9/search/SearchAccount.java
deleted file mode 100644
index e6b0cb36e..000000000
--- a/app/core/src/main/java/com/fsck/k9/search/SearchAccount.java
+++ /dev/null
@@ -1,80 +0,0 @@
-package com.fsck.k9.search;
-
-
-import com.fsck.k9.BaseAccount;
-import com.fsck.k9.CoreResourceProvider;
-import com.fsck.k9.DI;
-import com.fsck.k9.search.SearchSpecification.Attribute;
-import com.fsck.k9.search.SearchSpecification.SearchField;
-
-
-/**
- * This class is basically a wrapper around a LocalSearch. It allows to expose it as
- * an account. This is a meta-account containing all the email that matches the search.
- */
-public class SearchAccount implements BaseAccount {
-    public static final String UNIFIED_INBOX = "unified_inbox";
-    public static final String NEW_MESSAGES = "new_messages";
-
-
-    // create the unified inbox meta account ( all accounts is default when none specified )
-    public static SearchAccount createUnifiedInboxAccount() {
-        CoreResourceProvider resourceProvider = DI.get(CoreResourceProvider.class);
-        LocalSearch tmpSearch = new LocalSearch();
-        tmpSearch.setId(UNIFIED_INBOX);
-        tmpSearch.and(SearchField.INTEGRATE, "1", Attribute.EQUALS);
-        return new SearchAccount(UNIFIED_INBOX, tmpSearch, resourceProvider.searchUnifiedInboxTitle(),
-                resourceProvider.searchUnifiedInboxDetail());
-    }
-
-    private String mId;
-    private String mEmail;
-    private String name;
-    private LocalSearch mSearch;
-
-    public SearchAccount(String id, LocalSearch search, String name, String email)
-            throws IllegalArgumentException {
-
-        if (search == null) {
-            throw new IllegalArgumentException("Provided LocalSearch was null");
-        }
-
-        mId = id;
-        mSearch = search;
-        this.name = name;
-        mEmail = email;
-    }
-
-    public String getId() {
-        return mId;
-    }
-
-    @Override
-    public synchronized String getEmail() {
-        return mEmail;
-    }
-
-    @Override
-    public String getName() {
-        return name;
-    }
-
-    public LocalSearch getRelatedSearch() {
-        return mSearch;
-    }
-
-    /**
-     * Returns the ID of this {@code SearchAccount} instance.
-     *
-     * <p>
-     * This isn't really a UUID. But since we don't expose this value to other apps and we only
-     * use the account UUID as opaque string (e.g. as key in a {@code Map}) we're fine.<br>
-     * Using a constant string is necessary to identify the same search account even when the
-     * corresponding {@link SearchAccount} object has been recreated.
-     * </p>
-     */
-    @Override
-    public String getUuid() {
-        return mId;
-    }
-}
diff --git a/app/core/src/main/java/com/fsck/k9/search/SearchAccount.kt b/app/core/src/main/java/com/fsck/k9/search/SearchAccount.kt
new file mode 100644
index 000000000..68a7abea6
--- /dev/null
+++ b/app/core/src/main/java/com/fsck/k9/search/SearchAccount.kt
@@ -0,0 +1,53 @@
+package com.fsck.k9.search
+
+import com.fsck.k9.BaseAccount
+import com.fsck.k9.CoreResourceProvider
+import com.fsck.k9.search.SearchSpecification.SearchField
+import org.koin.core.component.KoinComponent
+import org.koin.core.component.inject
+
+/**
+ * This class is basically a wrapper around a LocalSearch. It allows to expose it as an account.
+ * This is a meta-account containing all the messages that match the search.
+ */
+class SearchAccount(
+    val id: String,
+    search: LocalSearch,
+    override val name: String,
+    override val email: String
+) : BaseAccount {
+    /**
+     * Returns the ID of this `SearchAccount` instance.
+     *
+     * This isn't really a UUID. But since we don't expose this value to other apps and we only use the account UUID
+     * as opaque string (e.g. as key in a `Map`) we're fine.
+     *
+     * Using a constant string is necessary to identify the same search account even when the corresponding
+     * [SearchAccount] object has been recreated.
+     */
+    override val uuid: String = id
+
+    val relatedSearch: LocalSearch = search
+
+    companion object : KoinComponent {
+        private val resourceProvider: CoreResourceProvider by inject()
+
+        const val UNIFIED_INBOX = "unified_inbox"
+        const val NEW_MESSAGES = "new_messages"
+
+        @JvmStatic
+        fun createUnifiedInboxAccount(): SearchAccount {
+            val tmpSearch = LocalSearch().apply {
+                id = UNIFIED_INBOX
+                and(SearchField.INTEGRATE, "1", SearchSpecification.Attribute.EQUALS)
+            }
+
+            return SearchAccount(
+                id = UNIFIED_INBOX,
+                search = tmpSearch,
+                name = resourceProvider.searchUnifiedInboxTitle(),
+                email = resourceProvider.searchUnifiedInboxDetail()
+            )
+        }
+    }
+}
diff --git a/app/core/src/test/java/com/fsck/k9/helper/IdentityHelperTest.kt b/app/core/src/test/java/com/fsck/k9/helper/IdentityHelperTest.kt
index 7bae4690d..cb2867043 100644
--- a/app/core/src/test/java/com/fsck/k9/helper/IdentityHelperTest.kt
+++ b/app/core/src/test/java/com/fsck/k9/helper/IdentityHelperTest.kt
@@ -115,13 +115,15 @@ class IdentityHelperTest : RobolectricTest() {
     }
 
     private fun createDummyAccount() = Account(UUID.randomUUID().toString()).apply {
-        identities = listOf(
-            newIdentity("Default", DEFAULT_ADDRESS),
-            newIdentity("Identity 1", IDENTITY_1_ADDRESS),
-            newIdentity("Identity 2", IDENTITY_2_ADDRESS),
-            newIdentity("Identity 3", IDENTITY_3_ADDRESS),
-            newIdentity("Identity 4", IDENTITY_4_ADDRESS),
-            newIdentity("Identity 5", IDENTITY_5_ADDRESS)
+        replaceIdentities(
+            listOf(
+                newIdentity("Default", DEFAULT_ADDRESS),
+                newIdentity("Identity 1", IDENTITY_1_ADDRESS),
+                newIdentity("Identity 2", IDENTITY_2_ADDRESS),
+                newIdentity("Identity 3", IDENTITY_3_ADDRESS),
+                newIdentity("Identity 4", IDENTITY_4_ADDRESS),
+                newIdentity("Identity 5", IDENTITY_5_ADDRESS)
+            )
         )
     }
 
diff --git a/app/core/src/test/java/com/fsck/k9/notification/BaseNotificationDataCreatorTest.kt b/app/core/src/test/java/com/fsck/k9/notification/BaseNotificationDataCreatorTest.kt
index 3ec3c6e8d..749d529d4 100644
--- a/app/core/src/test/java/com/fsck/k9/notification/BaseNotificationDataCreatorTest.kt
+++ b/app/core/src/test/java/com/fsck/k9/notification/BaseNotificationDataCreatorTest.kt
@@ -4,7 +4,8 @@ import com.fsck.k9.Account
 import com.fsck.k9.Identity
 import com.fsck.k9.K9
 import com.fsck.k9.K9.LockScreenNotificationVisibility
-import com.fsck.k9.NotificationSetting
+import com.fsck.k9.NotificationSettings
+import com.fsck.k9.VibratePattern
 import com.google.common.truth.Truth.assertThat
 import org.junit.Test
 import org.mockito.kotlin.mock
@@ -138,7 +139,7 @@ class BaseNotificationDataCreatorTest {
 
     @Test
     fun ringtone() {
-        account.notificationSetting.ringtone = "content://ringtone/1"
+        account.updateNotificationSettings { it.copy(ringtone = "content://ringtone/1") }
         val notificationData = createNotificationData()
 
         val result = notificationDataCreator.createBaseNotificationData(notificationData)
@@ -148,19 +149,21 @@ class BaseNotificationDataCreatorTest {
 
     @Test
     fun `vibration pattern`() {
-        account.notificationSetting.isVibrateEnabled = true
-        account.notificationSetting.vibratePattern = 3
-        account.notificationSetting.vibrateTimes = 2
+        account.updateNotificationSettings {
+            it.copy(isVibrateEnabled = true, vibratePattern = VibratePattern.Pattern3, vibrateTimes = 2)
+        }
         val notificationData = createNotificationData()
 
         val result = notificationDataCreator.createBaseNotificationData(notificationData)
 
-        assertThat(result.appearance.vibrationPattern).isEqualTo(NotificationSetting.getVibration(3, 2))
+        assertThat(result.appearance.vibrationPattern).isEqualTo(
+            NotificationSettings.getVibrationPattern(VibratePattern.Pattern3, 2)
+        )
     }
 
     @Test
     fun `led color`() {
-        account.notificationSetting.ledColor = 0x00FF00
+        account.updateNotificationSettings { it.copy(ledColor = 0x00FF00) }
         val notificationData = createNotificationData()
 
         val result = notificationDataCreator.createBaseNotificationData(notificationData)
@@ -192,7 +195,7 @@ class BaseNotificationDataCreatorTest {
     private fun createAccount(): Account {
         return Account("00000000-0000-4000-0000-000000000000").apply {
             name = "account name"
-            identities = listOf(Identity())
+            replaceIdentities(listOf(Identity()))
         }
     }
 }
diff --git a/app/k9mail/src/main/java/com/fsck/k9/widget/unread/UnreadWidgetDataProvider.kt b/app/k9mail/src/main/java/com/fsck/k9/widget/unread/UnreadWidgetDataProvider.kt
index 4766a43be..5690639c1 100644
--- a/app/k9mail/src/main/java/com/fsck/k9/widget/unread/UnreadWidgetDataProvider.kt
+++ b/app/k9mail/src/main/java/com/fsck/k9/widget/unread/UnreadWidgetDataProvider.kt
@@ -35,7 +35,7 @@ class UnreadWidgetDataProvider(
 
     private fun loadSearchAccountData(configuration: UnreadWidgetConfiguration): UnreadWidgetData {
         val searchAccount = getSearchAccount(configuration.accountUuid)
-        val title = searchAccount.name
+        val title = searchAccount.name ?: searchAccount.email
         val unreadCount = messagingController.getUnreadMessageCount(searchAccount)
         val clickIntent = MessageList.intentDisplaySearch(context, searchAccount.relatedSearch, false, true, true)
 
diff --git a/app/ui/legacy/src/main/java/com/fsck/k9/ui/BundleExtensions.kt b/app/ui/legacy/src/main/java/com/fsck/k9/ui/BundleExtensions.kt
index b062cf3cf..efb906f7e 100644
--- a/app/ui/legacy/src/main/java/com/fsck/k9/ui/BundleExtensions.kt
+++ b/app/ui/legacy/src/main/java/com/fsck/k9/ui/BundleExtensions.kt
@@ -10,3 +10,8 @@ inline fun <reified T : Enum<T>> Bundle.getEnum(key: String, defaultValue: T): T
     val value = getString(key) ?: return defaultValue
     return enumValueOf(value)
 }
+
+inline fun <reified T : Enum<T>> Bundle.getEnum(key: String): T {
+    val value = getString(key) ?: error("Missing enum value for key '$key'")
+    return enumValueOf(value)
+}
diff --git a/app/ui/legacy/src/main/java/com/fsck/k9/ui/settings/account/AccountSettingsDataStore.kt b/app/ui/legacy/src/main/java/com/fsck/k9/ui/settings/account/AccountSettingsDataStore.kt
index eebf6d7cd..28574489d 100644
--- a/app/ui/legacy/src/main/java/com/fsck/k9/ui/settings/account/AccountSettingsDataStore.kt
+++ b/app/ui/legacy/src/main/java/com/fsck/k9/ui/settings/account/AccountSettingsDataStore.kt
@@ -30,7 +30,7 @@ class AccountSettingsDataStore(
             "account_notify" -> account.isNotifyNewMail
             "account_notify_self" -> account.isNotifySelfNewMail
             "account_notify_contacts_mail_only" -> account.isNotifyContactsMailOnly
-            "account_led" -> account.notificationSetting.isLedEnabled
+            "account_led" -> account.notificationSettings.isLedEnabled
             "account_notify_sync" -> account.isNotifySync
             "openpgp_hide_sign_only" -> account.isOpenPgpHideSignOnly
             "openpgp_encrypt_subject" -> account.isOpenPgpEncryptSubject
@@ -55,7 +55,7 @@ class AccountSettingsDataStore(
             "account_notify" -> account.isNotifyNewMail = value
             "account_notify_self" -> account.isNotifySelfNewMail = value
             "account_notify_contacts_mail_only" -> account.isNotifyContactsMailOnly = value
-            "account_led" -> account.notificationSetting.setLed(value)
+            "account_led" -> account.updateNotificationSettings { it.copy(isLedEnabled = value) }
             "account_notify_sync" -> account.isNotifySync = value
             "openpgp_hide_sign_only" -> account.isOpenPgpHideSignOnly = value
             "openpgp_encrypt_subject" -> account.isOpenPgpEncryptSubject = value
@@ -72,7 +72,7 @@ class AccountSettingsDataStore(
     override fun getInt(key: String?, defValue: Int): Int {
         return when (key) {
             "chip_color" -> account.chipColor
-            "led_color" -> account.notificationSetting.ledColor
+            "led_color" -> account.notificationSettings.ledColor
             else -> defValue
         }
     }
@@ -134,7 +134,7 @@ class AccountSettingsDataStore(
             "folder_notify_new_mail_mode" -> account.folderNotifyNewMailMode.name
             "account_combined_vibration" -> getCombinedVibrationValue()
             "account_remote_search_num_results" -> account.remoteSearchNumResults.toString()
-            "account_ringtone" -> account.notificationSetting.ringtone
+            "account_ringtone" -> account.notificationSettings.ringtone
             else -> defValue
         }
     }
@@ -149,12 +149,12 @@ class AccountSettingsDataStore(
             "account_message_age" -> account.maximumPolledMessageAge = value.toInt()
             "account_autodownload_size" -> account.maximumAutoDownloadMessageSize = value.toInt()
             "account_check_frequency" -> {
-                if (account.setAutomaticCheckIntervalMinutes(value.toInt())) {
+                if (account.updateAutomaticCheckIntervalMinutes(value.toInt())) {
                     reschedulePoll()
                 }
             }
             "folder_sync_mode" -> {
-                if (account.setFolderSyncMode(Account.FolderMode.valueOf(value))) {
+                if (account.updateFolderSyncMode(Account.FolderMode.valueOf(value))) {
                     reschedulePoll()
                 }
             }
@@ -178,10 +178,7 @@ class AccountSettingsDataStore(
             "folder_notify_new_mail_mode" -> account.folderNotifyNewMailMode = Account.FolderMode.valueOf(value)
             "account_combined_vibration" -> setCombinedVibrationValue(value)
             "account_remote_search_num_results" -> account.remoteSearchNumResults = value.toInt()
-            "account_ringtone" -> with(account.notificationSetting) {
-                isRingEnabled = true
-                ringtone = value
-            }
+            "account_ringtone" -> account.updateNotificationSettings { it.copy(isRingEnabled = true, ringtone = value) }
             else -> return
         }
 
@@ -189,8 +186,8 @@ class AccountSettingsDataStore(
     }
 
     private fun setNotificationLightColor(value: Int) {
-        if (account.notificationSetting.ledColor != value) {
-            account.notificationSetting.ledColor = value
+        if (account.notificationSettings.ledColor != value) {
+            account.updateNotificationSettings { it.copy(ledColor = value) }
             notificationSettingsChanged = true
         }
     }
@@ -245,17 +242,21 @@ class AccountSettingsDataStore(
 
     private fun getCombinedVibrationValue(): String {
         return VibrationPreference.encode(
-            isVibrationEnabled = account.notificationSetting.isVibrateEnabled,
-            vibrationPattern = account.notificationSetting.vibratePattern,
-            vibrationTimes = account.notificationSetting.vibrateTimes
+            isVibrationEnabled = account.notificationSettings.isVibrateEnabled,
+            vibratePattern = account.notificationSettings.vibratePattern,
+            vibrationTimes = account.notificationSettings.vibrateTimes
         )
     }
 
     private fun setCombinedVibrationValue(value: String) {
         val (isVibrationEnabled, vibrationPattern, vibrationTimes) = VibrationPreference.decode(value)
-        account.notificationSetting.isVibrateEnabled = isVibrationEnabled
-        account.notificationSetting.vibratePattern = vibrationPattern
-        account.notificationSetting.vibrateTimes = vibrationTimes
+        account.updateNotificationSettings { notificationSettings ->
+            notificationSettings.copy(
+                isVibrateEnabled = isVibrationEnabled,
+                vibratePattern = vibrationPattern,
+                vibrateTimes = vibrationTimes,
+            )
+        }
         notificationSettingsChanged = true
     }
 }
diff --git a/app/ui/legacy/src/main/java/com/fsck/k9/ui/settings/account/VibrationDialogFragment.kt b/app/ui/legacy/src/main/java/com/fsck/k9/ui/settings/account/VibrationDialogFragment.kt
index b9ba9e99c..d978d2c3b 100644
--- a/app/ui/legacy/src/main/java/com/fsck/k9/ui/settings/account/VibrationDialogFragment.kt
+++ b/app/ui/legacy/src/main/java/com/fsck/k9/ui/settings/account/VibrationDialogFragment.kt
@@ -16,8 +16,11 @@ import androidx.appcompat.app.AlertDialog
 import androidx.appcompat.widget.SwitchCompat
 import androidx.core.content.getSystemService
 import androidx.preference.PreferenceDialogFragmentCompat
-import com.fsck.k9.NotificationSetting
+import com.fsck.k9.NotificationSettings
+import com.fsck.k9.VibratePattern
 import com.fsck.k9.ui.R
+import com.fsck.k9.ui.getEnum
+import com.fsck.k9.ui.putEnum
 
 class VibrationDialogFragment : PreferenceDialogFragmentCompat() {
     private val vibrator by lazy { requireContext().getSystemService<Vibrator>() ?: error("Vibrator service missing") }
@@ -31,15 +34,15 @@ class VibrationDialogFragment : PreferenceDialogFragmentCompat() {
         val context = requireContext()
 
         val isVibrationEnabled: Boolean
-        val vibrationPattern: Int
+        val vibratePattern: VibratePattern
         val vibrationTimes: Int
         if (savedInstanceState != null) {
             isVibrationEnabled = savedInstanceState.getBoolean(STATE_VIBRATE)
-            vibrationPattern = savedInstanceState.getInt(STATE_VIBRATION_PATTERN)
+            vibratePattern = savedInstanceState.getEnum(STATE_VIBRATE_PATTERN)
             vibrationTimes = savedInstanceState.getInt(STATE_VIBRATION_TIMES)
         } else {
             isVibrationEnabled = vibrationPreference.isVibrationEnabled
-            vibrationPattern = vibrationPreference.vibrationPattern
+            vibratePattern = vibrationPreference.vibratePattern
             vibrationTimes = vibrationPreference.vibrationTimes
         }
 
@@ -47,7 +50,7 @@ class VibrationDialogFragment : PreferenceDialogFragmentCompat() {
             isVibrationEnabled,
             entries = vibrationPreference.entries.map { it.toString() },
             entryValues = vibrationPreference.entryValues.map { it.toString().toInt() },
-            vibrationPattern,
+            vibratePattern,
             vibrationTimes
         )
 
@@ -62,7 +65,7 @@ class VibrationDialogFragment : PreferenceDialogFragmentCompat() {
         if (positiveResult) {
             vibrationPreference.setVibration(
                 isVibrationEnabled = adapter.isVibrationEnabled,
-                vibrationPattern = adapter.vibrationPattern,
+                vibratePattern = adapter.vibratePattern,
                 vibrationTimes = adapter.vibrationTimes
             )
         }
@@ -71,21 +74,21 @@ class VibrationDialogFragment : PreferenceDialogFragmentCompat() {
     override fun onSaveInstanceState(outState: Bundle) {
         super.onSaveInstanceState(outState)
         outState.putBoolean(STATE_VIBRATE, adapter.isVibrationEnabled)
-        outState.putInt(STATE_VIBRATION_PATTERN, adapter.vibrationPattern)
+        outState.putEnum(STATE_VIBRATE_PATTERN, adapter.vibratePattern)
         outState.putInt(STATE_VIBRATION_TIMES, adapter.vibrationTimes)
     }
 
     private fun playVibration() {
-        val vibrationPattern = adapter.vibrationPattern
+        val vibratePattern = adapter.vibratePattern
         val vibrationTimes = adapter.vibrationTimes
-        val combinedPattern = NotificationSetting.getVibration(vibrationPattern, vibrationTimes)
+        val vibrationPattern = NotificationSettings.getVibrationPattern(vibratePattern, vibrationTimes)
 
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
-            val vibrationEffect = VibrationEffect.createWaveform(combinedPattern, -1)
+            val vibrationEffect = VibrationEffect.createWaveform(vibrationPattern, -1)
             vibrator.vibrate(vibrationEffect)
         } else {
             @Suppress("DEPRECATION")
-            vibrator.vibrate(combinedPattern, -1)
+            vibrator.vibrate(vibrationPattern, -1)
         }
     }
 
@@ -93,13 +96,13 @@ class VibrationDialogFragment : PreferenceDialogFragmentCompat() {
         var isVibrationEnabled: Boolean,
         private val entries: List<String>,
         private val entryValues: List<Int>,
-        initialVibrationPattern: Int,
+        initialVibratePattern: VibratePattern,
         initialVibrationTimes: Int
     ) : BaseAdapter() {
-        private var checkedEntryIndex = entryValues.indexOf(initialVibrationPattern).takeIf { it != -1 } ?: 0
+        private var checkedEntryIndex = entryValues.indexOf(initialVibratePattern.serialize()).takeIf { it != -1 } ?: 0
 
-        val vibrationPattern: Int
-            get() = entryValues[checkedEntryIndex]
+        val vibratePattern: VibratePattern
+            get() = VibratePattern.deserialize(entryValues[checkedEntryIndex])
 
         var vibrationTimes = initialVibrationTimes
 
@@ -209,7 +212,7 @@ class VibrationDialogFragment : PreferenceDialogFragmentCompat() {
 
     companion object {
         private const val STATE_VIBRATE = "vibrate"
-        private const val STATE_VIBRATION_PATTERN = "vibrationPattern"
+        private const val STATE_VIBRATE_PATTERN = "vibratePattern"
         private const val STATE_VIBRATION_TIMES = "vibrationTimes"
     }
 }
diff --git a/app/ui/legacy/src/main/java/com/fsck/k9/ui/settings/account/VibrationPreference.kt b/app/ui/legacy/src/main/java/com/fsck/k9/ui/settings/account/VibrationPreference.kt
index 2cbd33405..825f75a85 100644
--- a/app/ui/legacy/src/main/java/com/fsck/k9/ui/settings/account/VibrationPreference.kt
+++ b/app/ui/legacy/src/main/java/com/fsck/k9/ui/settings/account/VibrationPreference.kt
@@ -5,7 +5,8 @@ import android.content.Context
 import android.util.AttributeSet
 import androidx.core.content.res.TypedArrayUtils
 import androidx.preference.ListPreference
-import com.fsck.k9.NotificationSetting
+import com.fsck.k9.NotificationSettings
+import com.fsck.k9.VibratePattern
 import com.fsck.k9.ui.R
 import com.takisoft.preferencex.PreferenceFragmentCompat
 
@@ -28,7 +29,7 @@ constructor(
     internal var isVibrationEnabled: Boolean = false
         private set
 
-    internal var vibrationPattern: Int = DEFAULT_VIBRATION_PATTERN
+    internal var vibratePattern = DEFAULT_VIBRATE_PATTERN
         private set
 
     internal var vibrationTimes: Int = DEFAULT_VIBRATION_TIMES
@@ -39,7 +40,7 @@ constructor(
         val (isVibrationEnabled, vibrationPattern, vibrationTimes) = decode(encoded)
 
         this.isVibrationEnabled = isVibrationEnabled
-        this.vibrationPattern = vibrationPattern
+        this.vibratePattern = vibrationPattern
         this.vibrationTimes = vibrationTimes
 
         updateSummary()
@@ -49,12 +50,12 @@ constructor(
         preferenceManager.showDialog(this)
     }
 
-    fun setVibration(isVibrationEnabled: Boolean, vibrationPattern: Int, vibrationTimes: Int) {
+    fun setVibration(isVibrationEnabled: Boolean, vibratePattern: VibratePattern, vibrationTimes: Int) {
         this.isVibrationEnabled = isVibrationEnabled
-        this.vibrationPattern = vibrationPattern
+        this.vibratePattern = vibratePattern
         this.vibrationTimes = vibrationTimes
 
-        val encoded = encode(isVibrationEnabled, vibrationPattern, vibrationTimes)
+        val encoded = encode(isVibrationEnabled, vibratePattern, vibrationTimes)
         persistString(encoded)
 
         updateSummary()
@@ -62,26 +63,29 @@ constructor(
 
     fun setVibrationFromSystem(isVibrationEnabled: Boolean, combinedPattern: List<Long>?) {
         if (combinedPattern == null || combinedPattern.size < 2 || combinedPattern.size % 2 != 0) {
-            setVibration(isVibrationEnabled, DEFAULT_VIBRATION_PATTERN, DEFAULT_VIBRATION_TIMES)
+            setVibration(isVibrationEnabled, DEFAULT_VIBRATE_PATTERN, DEFAULT_VIBRATION_TIMES)
             return
         }
 
         val combinedPatternArray = combinedPattern.toLongArray()
         val vibrationTimes = combinedPattern.size / 2
         val vibrationPattern = entryValues.asSequence()
-            .map { entryValue -> entryValue.toString().toInt() }
-            .firstOrNull { vibrationPattern ->
-                val testPattern = NotificationSetting.getVibration(vibrationPattern, vibrationTimes)
+            .map { entryValue ->
+                val serializedVibratePattern = entryValue.toString().toInt()
+                VibratePattern.deserialize(serializedVibratePattern)
+            }
+            .firstOrNull { vibratePattern ->
+                val testPattern = NotificationSettings.getVibrationPattern(vibratePattern, vibrationTimes)
 
                 testPattern.contentEquals(combinedPatternArray)
-            } ?: DEFAULT_VIBRATION_PATTERN
+            } ?: DEFAULT_VIBRATE_PATTERN
 
         setVibration(isVibrationEnabled, vibrationPattern, vibrationTimes)
     }
 
     private fun updateSummary() {
         summary = if (isVibrationEnabled) {
-            val index = entryValues.indexOf(vibrationPattern.toString())
+            val index = entryValues.indexOf(vibratePattern.serialize().toString())
             entries[index]
         } else {
             context.getString(R.string.account_settings_vibrate_summary_disabled)
@@ -89,7 +93,7 @@ constructor(
     }
 
     companion object {
-        private const val DEFAULT_VIBRATION_PATTERN = 0
+        private val DEFAULT_VIBRATE_PATTERN = VibratePattern.Default
         private const val DEFAULT_VIBRATION_TIMES = 1
 
         init {
@@ -98,14 +102,14 @@ constructor(
             )
         }
 
-        fun encode(isVibrationEnabled: Boolean, vibrationPattern: Int, vibrationTimes: Int): String {
-            return "$isVibrationEnabled|$vibrationPattern|$vibrationTimes"
+        fun encode(isVibrationEnabled: Boolean, vibratePattern: VibratePattern, vibrationTimes: Int): String {
+            return "$isVibrationEnabled|${vibratePattern.name}|$vibrationTimes"
         }
 
-        fun decode(encoded: String): Triple<Boolean, Int, Int> {
+        fun decode(encoded: String): Triple<Boolean, VibratePattern, Int> {
             val parts = encoded.split('|')
             val isVibrationEnabled = parts[0].toBoolean()
-            val vibrationPattern = parts[1].toInt()
+            val vibrationPattern = VibratePattern.valueOf(parts[1])
             val vibrationTimes = parts[2].toInt()
             return Triple(isVibrationEnabled, vibrationPattern, vibrationTimes)
         }