diff --git a/app/k9mail/build.gradle b/app/k9mail/build.gradle
index c93bdcb03..81df0b2c3 100644
--- a/app/k9mail/build.gradle
+++ b/app/k9mail/build.gradle
@@ -47,7 +47,7 @@ android {
         minSdkVersion buildConfig.minSdk
         targetSdkVersion buildConfig.targetSdk
 
-        generatedDensities = ['mdpi', 'hdpi', 'xhdpi']
+        vectorDrawables.useSupportLibrary = true
 
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
diff --git a/app/ui/src/main/res/layout/account_list_item.xml b/app/ui/src/main/res/layout/account_list_item.xml
index d131e49cc..6edede8f2 100644
--- a/app/ui/src/main/res/layout/account_list_item.xml
+++ b/app/ui/src/main/res/layout/account_list_item.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
@@ -15,7 +16,7 @@
         android:layout_height="40dp"
         android:contentDescription="@string/account_settings_action"
         android:padding="8dp"
-        android:src="?attr/iconSettingsAccount" />
+        app:srcCompat="?attr/iconSettingsAccount" />
 
     <LinearLayout
         android:layout_width="match_parent"
diff --git a/app/ui/src/main/res/layout/accounts_item.xml b/app/ui/src/main/res/layout/accounts_item.xml
index 41eb959f1..fc45e6f2f 100644
--- a/app/ui/src/main/res/layout/accounts_item.xml
+++ b/app/ui/src/main/res/layout/accounts_item.xml
@@ -2,6 +2,7 @@
 <LinearLayout
         android:id="@+id/accounts_item_layout"
         xmlns:android="http://schemas.android.com/apk/res/android"
+        xmlns:app="http://schemas.android.com/apk/res-auto"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:minHeight="?android:attr/listPreferredItemHeight"
@@ -67,7 +68,7 @@
                 android:gravity="center_vertical"
                 android:focusable="false"
                 android:layout_marginRight="3dip"
-                android:src="?attr/iconFolder"
+                app:srcCompat="?attr/iconFolder"
                 android:background="?selectableItemBackground"
                 android:layout_width="wrap_content"
                 android:layout_height="fill_parent"
diff --git a/app/ui/src/main/res/layout/choose_folder_list_item.xml b/app/ui/src/main/res/layout/choose_folder_list_item.xml
index fe6fe00e9..27ca5c2d6 100644
--- a/app/ui/src/main/res/layout/choose_folder_list_item.xml
+++ b/app/ui/src/main/res/layout/choose_folder_list_item.xml
@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout
         xmlns:android="http://schemas.android.com/apk/res/android"
+        xmlns:app="http://schemas.android.com/apk/res-auto"
         xmlns:tools="http://schemas.android.com/tools"
         android:id="@+id/folder_list_item_layout"
         android:layout_width="match_parent"
@@ -15,7 +16,7 @@
             android:layout_height="24dp"
             android:layout_marginStart="16dp"
             android:layout_marginEnd="32dp"
-            android:src="@drawable/ic_drafts_folder_light"/>
+            app:srcCompat="@drawable/ic_drafts_folder_light"/>
 
     <TextView
             android:id="@+id/folder_name"
diff --git a/app/ui/src/main/res/layout/client_certificate_spinner.xml b/app/ui/src/main/res/layout/client_certificate_spinner.xml
index 690b6dd02..a2a20bb3d 100644
--- a/app/ui/src/main/res/layout/client_certificate_spinner.xml
+++ b/app/ui/src/main/res/layout/client_certificate_spinner.xml
@@ -1,5 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
-<merge xmlns:android="http://schemas.android.com/apk/res/android" >
+<merge
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
 
     <Button
         android:id="@+id/client_certificate_spinner_button"
@@ -17,6 +19,6 @@
         android:background="?selectableItemBackground"
         android:contentDescription="@string/client_certificate_spinner_delete"
         android:padding="8dp"
-        android:src="?attr/iconActionCancel" />
+        app:srcCompat="?attr/iconActionCancel" />
 
-</merge>
\ No newline at end of file
+</merge>
diff --git a/app/ui/src/main/res/layout/foldable_linearlayout.xml b/app/ui/src/main/res/layout/foldable_linearlayout.xml
index fafa3074d..7b684afdd 100644
--- a/app/ui/src/main/res/layout/foldable_linearlayout.xml
+++ b/app/ui/src/main/res/layout/foldable_linearlayout.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical" >
@@ -18,7 +19,7 @@
             android:layout_height="wrap_content"
             android:layout_gravity="center_vertical"
             android:layout_marginRight="10dp"
-            android:src="?attr/iconActionExpand" />
+            app:srcCompat="?attr/iconActionExpand" />
 
         <TextView
             android:id="@+id/foldableText"
@@ -36,4 +37,4 @@
         android:orientation="vertical"
         android:visibility="invisible" />
 
-</LinearLayout>
\ No newline at end of file
+</LinearLayout>
diff --git a/app/ui/src/main/res/layout/folder_list_item.xml b/app/ui/src/main/res/layout/folder_list_item.xml
index ab9dc3699..61b48cd1e 100644
--- a/app/ui/src/main/res/layout/folder_list_item.xml
+++ b/app/ui/src/main/res/layout/folder_list_item.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:id="@+id/folder_list_item_layout"
     android:layout_width="match_parent"
@@ -17,7 +18,7 @@
         android:layout_height="24dp"
         android:layout_marginStart="16dp"
         android:layout_marginEnd="32dp"
-        android:src="@drawable/ic_drafts_folder_light" />
+        app:srcCompat="@drawable/ic_drafts_folder_light" />
 
     <TextView
         android:id="@+id/folder_name"
diff --git a/app/ui/src/main/res/layout/fragment_about.xml b/app/ui/src/main/res/layout/fragment_about.xml
index ad875fc57..13c72a40c 100644
--- a/app/ui/src/main/res/layout/fragment_about.xml
+++ b/app/ui/src/main/res/layout/fragment_about.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+              xmlns:app="http://schemas.android.com/apk/res-auto"
               android:orientation="vertical"
               android:layout_height="fill_parent"
               android:layout_width="fill_parent">
@@ -14,7 +15,7 @@
                   android:layout_width="fill_parent">
 
             <ImageView
-                    android:src="@mipmap/icon"
+                    app:srcCompat="@mipmap/icon"
                     android:layout_width="100dp"
                     android:layout_height="100dp"
                     android:layout_gravity="center"
@@ -44,7 +45,7 @@
                     android:focusable="true"
                     android:background="?attr/selectableItemBackground">
                 <ImageView
-                        android:src="?attr/iconSettingsAbout"
+                        app:srcCompat="?attr/iconSettingsAbout"
                         android:layout_width="24dp"
                         android:layout_height="24dp"
                         android:layout_gravity="center" />
@@ -81,7 +82,7 @@
                     android:focusable="true"
                     android:background="?attr/selectableItemBackground">
                 <ImageView
-                        android:src="?attr/iconAboutAuthors"
+                        app:srcCompat="?attr/iconAboutAuthors"
                         android:layout_width="24dp"
                         android:layout_height="24dp"
                         android:layout_gravity="center" />
@@ -118,7 +119,7 @@
                     android:focusable="true"
                     android:background="?attr/selectableItemBackground">
                 <ImageView
-                        android:src="?attr/iconAboutLicense"
+                        app:srcCompat="?attr/iconAboutLicense"
                         android:layout_width="24dp"
                         android:layout_height="24dp"
                         android:layout_gravity="center" />
diff --git a/app/ui/src/main/res/layout/message_compose_attachment.xml b/app/ui/src/main/res/layout/message_compose_attachment.xml
index 77a94f8c0..84aba9911 100644
--- a/app/ui/src/main/res/layout/message_compose_attachment.xml
+++ b/app/ui/src/main/res/layout/message_compose_attachment.xml
@@ -36,7 +36,7 @@
             android:layout_marginTop="8dp"
             android:layout_marginBottom="8dp"
             android:contentDescription="@null"
-            android:src="@drawable/ic_attachment_generic"
+            app:srcCompat="@drawable/ic_attachment_generic"
             app:layout_constraintBottom_toBottomOf="parent"
             app:layout_constraintStart_toStartOf="parent"
             app:layout_constraintTop_toBottomOf="@+id/attachment_preview"
@@ -101,7 +101,7 @@
             android:layout_marginBottom="8dp"
             android:background="?attr/selectableItemBackgroundBorderless"
             android:contentDescription="@string/remove_attachment_action"
-            android:src="?attr/iconActionCancel"
+            app:srcCompat="?attr/iconActionCancel"
             app:layout_constraintBottom_toBottomOf="parent"
             app:layout_constraintEnd_toEndOf="parent"
             app:layout_constraintTop_toBottomOf="@+id/attachment_preview" />
diff --git a/app/ui/src/main/res/layout/message_compose_recipients.xml b/app/ui/src/main/res/layout/message_compose_recipients.xml
index df38056bf..160b6ca38 100644
--- a/app/ui/src/main/res/layout/message_compose_recipients.xml
+++ b/app/ui/src/main/res/layout/message_compose_recipients.xml
@@ -1,13 +1,12 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout
     xmlns:tools="http://schemas.android.com/tools"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
-    xmlns:custom="http://schemas.android.com/apk/res-auto"
     android:layout_marginBottom="4dp"
-    android:orientation="vertical"
-    tools:showIn="@layout/message_compose">
+    android:orientation="vertical">
 
     <LinearLayout
         android:layout_width="match_parent"
@@ -54,7 +53,7 @@
             tools:visibility="visible"
             android:inAnimation="@anim/fade_in"
             android:outAnimation="@anim/fade_out"
-            custom:previewInitialChild="1">
+            app:previewInitialChild="1">
 
             <ImageView
                 android:layout_width="wrap_content"
@@ -62,7 +61,7 @@
                 android:layout_gravity="center_vertical"
                 android:layout_margin="8dp"
                 android:id="@+id/crypto_special_inline"
-                android:src="@drawable/compatibility"
+                app:srcCompat="@drawable/compatibility"
                 android:tint="@color/light_black"
                 />
 
@@ -72,7 +71,7 @@
                 android:layout_gravity="center"
                 android:layout_margin="8dp"
                 android:id="@+id/crypto_special_sign_only"
-                android:src="@drawable/status_signature"
+                app:srcCompat="@drawable/status_signature"
                 android:tint="?attr/openpgp_blue"
                 />
 
@@ -87,7 +86,7 @@
                     android:layout_height="wrap_content"
                     android:layout_gravity="center"
                     android:layout_margin="8dp"
-                    android:src="@drawable/status_signature"
+                    app:srcCompat="@drawable/status_signature"
                     android:tint="?attr/openpgp_blue"
                     />
 
@@ -95,7 +94,7 @@
                     android:layout_width="16dp"
                     android:layout_height="16dp"
                     android:layout_gravity="right|bottom"
-                    android:src="@drawable/compatibility"
+                    app:srcCompat="@drawable/compatibility"
                     android:tint="@color/light_black"
                     />
             </FrameLayout>
@@ -120,14 +119,14 @@
                 tools:visibility="visible"
                 android:inAnimation="@anim/fade_in"
                 android:outAnimation="@anim/fade_out"
-                custom:previewInitialChild="0">
+                app:previewInitialChild="0">
 
                 <ImageView
                     android:layout_width="wrap_content"
                     android:layout_height="wrap_content"
                     android:layout_gravity="center"
                     android:id="@+id/crypto_status_disabled"
-                    android:src="@drawable/status_lock_disabled"
+                    app:srcCompat="@drawable/status_lock_disabled"
                     android:tint="?attr/openpgp_dark_grey"
                     />
 
@@ -136,7 +135,7 @@
                     android:layout_height="wrap_content"
                     android:layout_gravity="center"
                     android:id="@+id/crypto_status_enabled"
-                    android:src="@drawable/status_lock"
+                    app:srcCompat="@drawable/status_lock"
                     android:tint="?attr/openpgp_green"
                     />
 
@@ -150,7 +149,7 @@
                         android:layout_width="wrap_content"
                         android:layout_height="wrap_content"
                         android:layout_gravity="left|center_vertical"
-                        android:src="@drawable/status_dots"
+                        app:srcCompat="@drawable/status_dots"
                         android:tint="?attr/openpgp_grey"
                         />
 
@@ -158,7 +157,7 @@
                         android:layout_width="wrap_content"
                         android:layout_height="wrap_content"
                         android:layout_gravity="left|center_vertical"
-                        android:src="@drawable/status_lock_dots_3"
+                        app:srcCompat="@drawable/status_lock_dots_3"
                         android:tint="?attr/openpgp_green"
                         />
 
@@ -169,7 +168,7 @@
                     android:layout_height="wrap_content"
                     android:layout_gravity="center"
                     android:id="@+id/crypto_status_error"
-                    android:src="@drawable/status_lock_error"
+                    app:srcCompat="@drawable/status_lock_error"
                     android:tint="?attr/openpgp_red"
                     />
 
@@ -242,7 +241,7 @@
                 android:layout_height="match_parent"
                 android:padding="6dp"
                 android:scaleType="centerCrop"
-                android:src="?attr/iconActionExpand"
+                app:srcCompat="?attr/iconActionExpand"
                 android:id="@+id/recipient_expander"
                 />
 
diff --git a/app/ui/src/main/res/layout/message_list_item.xml b/app/ui/src/main/res/layout/message_list_item.xml
index 8db2887cd..26a07ba37 100644
--- a/app/ui/src/main/res/layout/message_list_item.xml
+++ b/app/ui/src/main/res/layout/message_list_item.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+              xmlns:app="http://schemas.android.com/apk/res-auto"
               xmlns:tools="http://schemas.android.com/tools"
               android:layout_width="match_parent"
               android:layout_height="wrap_content"
@@ -28,7 +29,7 @@
             android:id="@+id/selected"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
-            android:src="@drawable/ic_check_circle_large"
+            app:srcCompat="@drawable/ic_check_circle_large"
             android:visibility="gone"
             android:contentDescription="@null" />
 
@@ -78,13 +79,13 @@
                 android:layout_height="wrap_content"
                 android:layout_gravity="center_vertical"
                 android:layout_marginEnd="4dp"
-                android:src="@drawable/ic_account_color" />
+                app:srcCompat="@drawable/ic_account_color" />
 
             <ImageView
                 android:id="@+id/status"
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
-                android:src="?attr/messageListAnswered"
+                app:srcCompat="?attr/messageListAnswered"
                 tools:src="@drawable/ic_messagelist_answered_light"/>
 
             <TextView
@@ -121,7 +122,7 @@
                 android:layout_height="wrap_content"
                 android:layout_alignTop="@+id/date"
                 android:layout_alignBottom="@+id/date"
-                android:src="?attr/messageListAttachment"
+                app:srcCompat="?attr/messageListAttachment"
                 android:layout_alignWithParentIfMissing="true"
                 android:layout_toStartOf="@+id/date" />
 
diff --git a/app/ui/src/main/res/layout/message_view_attachment.xml b/app/ui/src/main/res/layout/message_view_attachment.xml
index 61ede8729..66f4d9ac4 100644
--- a/app/ui/src/main/res/layout/message_view_attachment.xml
+++ b/app/ui/src/main/res/layout/message_view_attachment.xml
@@ -43,7 +43,7 @@
                 android:layout_marginTop="8dp"
                 android:layout_marginBottom="8dp"
                 android:contentDescription="@null"
-                android:src="@drawable/ic_attachment_generic"
+                app:srcCompat="@drawable/ic_attachment_generic"
                 app:layout_constraintBottom_toBottomOf="parent"
                 app:layout_constraintStart_toStartOf="parent"
                 app:layout_constraintTop_toBottomOf="@+id/attachment_preview"
@@ -90,7 +90,7 @@
                 android:layout_marginBottom="8dp"
                 android:background="?attr/selectableItemBackgroundBorderless"
                 android:contentDescription="@string/remove_attachment_action"
-                android:src="?attr/iconActionSave"
+                app:srcCompat="?attr/iconActionSave"
                 app:layout_constraintBottom_toBottomOf="parent"
                 app:layout_constraintEnd_toEndOf="parent"
                 app:layout_constraintTop_toBottomOf="@+id/attachment_preview" />
diff --git a/app/ui/src/main/res/layout/message_view_attachment_locked.xml b/app/ui/src/main/res/layout/message_view_attachment_locked.xml
index 291c904e1..28a51897c 100644
--- a/app/ui/src/main/res/layout/message_view_attachment_locked.xml
+++ b/app/ui/src/main/res/layout/message_view_attachment_locked.xml
@@ -31,7 +31,7 @@
                 android:layout_marginTop="8dp"
                 android:layout_marginBottom="8dp"
                 android:contentDescription="@null"
-                android:src="@drawable/status_signature_unknown"
+                app:srcCompat="@drawable/status_signature_unknown"
                 app:layout_constraintBottom_toBottomOf="parent"
                 app:layout_constraintStart_toStartOf="parent"
                 app:layout_constraintTop_toTopOf="parent"
@@ -76,7 +76,7 @@
                 android:layout_marginBottom="8dp"
                 android:background="?attr/selectableItemBackgroundBorderless"
                 android:contentDescription="@string/locked_attach_unlock"
-                android:src="?attr/unencryptedAttachmentUnlock"
+                app:srcCompat="?attr/unencryptedAttachmentUnlock"
                 app:layout_constraintBottom_toBottomOf="parent"
                 app:layout_constraintEnd_toEndOf="parent"
                 app:layout_constraintStart_toEndOf="@+id/locked_name"
diff --git a/app/ui/src/main/res/layout/message_view_header.xml b/app/ui/src/main/res/layout/message_view_header.xml
index 9099329fe..6bb29ddf8 100644
--- a/app/ui/src/main/res/layout/message_view_header.xml
+++ b/app/ui/src/main/res/layout/message_view_header.xml
@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <com.fsck.k9.view.MessageHeader
     xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:id="@+id/header_container"
     android:layout_width="match_parent"
@@ -50,7 +51,7 @@
                     android:layout_height="wrap_content"
                     android:layout_gravity="center"
                     android:padding="6dp"
-                    android:src="@drawable/status_lock_disabled"
+                    app:srcCompat="@drawable/status_lock_disabled"
                     android:tint="?attr/openpgp_grey"
                     android:background="?selectableItemBackground"
                     android:visibility="gone"
@@ -265,7 +266,7 @@
                             android:id="@+id/icon_single_message_options"
                             android:layout_width="wrap_content"
                             android:layout_height="wrap_content"
-                            android:src="?iconActionSingleMessageOptions"
+                            app:srcCompat="?iconActionSingleMessageOptions"
                             android:padding="8dp"
                             android:background="?selectableItemBackground"
                             />
diff --git a/app/ui/src/main/res/layout/openpgp_encrypt_description_dialog.xml b/app/ui/src/main/res/layout/openpgp_encrypt_description_dialog.xml
index 8381c82cf..6825c4dad 100644
--- a/app/ui/src/main/res/layout/openpgp_encrypt_description_dialog.xml
+++ b/app/ui/src/main/res/layout/openpgp_encrypt_description_dialog.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
@@ -20,7 +21,7 @@
             android:layout_width="wrap_content"
             android:layout_height="20dp"
             android:layout_gravity="center_vertical"
-            android:src="@drawable/status_signature"
+            app:srcCompat="@drawable/status_signature"
             android:scaleType="fitCenter"
             android:tint="@color/light_black"
             />
@@ -55,7 +56,7 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:padding="6dp"
-            android:src="@drawable/status_lock_disabled"
+            app:srcCompat="@drawable/status_lock_disabled"
             android:tint="?attr/openpgp_dark_grey"
             />
 
@@ -63,14 +64,14 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_gravity="center_vertical"
-            android:src="?attr/iconActionNextStatus"
+            app:srcCompat="?attr/iconActionNextStatus"
             />
 
         <ImageView
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:padding="6dp"
-            android:src="@drawable/status_lock"
+            app:srcCompat="@drawable/status_lock"
             android:tint="?attr/openpgp_green"
             />
 
@@ -94,4 +95,4 @@
         android:text="@string/openpgp_description_text3"
         />
 
-</LinearLayout>
\ No newline at end of file
+</LinearLayout>
diff --git a/app/ui/src/main/res/layout/openpgp_inline_dialog.xml b/app/ui/src/main/res/layout/openpgp_inline_dialog.xml
index b46ef2ad3..98724ac6b 100644
--- a/app/ui/src/main/res/layout/openpgp_inline_dialog.xml
+++ b/app/ui/src/main/res/layout/openpgp_inline_dialog.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
@@ -18,7 +19,7 @@
             android:layout_width="wrap_content"
             android:layout_height="20dp"
             android:layout_gravity="center_vertical"
-            android:src="@drawable/compatibility"
+            app:srcCompat="@drawable/compatibility"
             android:scaleType="fitCenter"
             android:tint="@color/light_black"
             />
@@ -116,4 +117,4 @@
 
     </LinearLayout>
 
-</LinearLayout>
\ No newline at end of file
+</LinearLayout>
diff --git a/app/ui/src/main/res/layout/openpgp_sign_only_dialog.xml b/app/ui/src/main/res/layout/openpgp_sign_only_dialog.xml
index f323e4d01..27134d5ed 100644
--- a/app/ui/src/main/res/layout/openpgp_sign_only_dialog.xml
+++ b/app/ui/src/main/res/layout/openpgp_sign_only_dialog.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
@@ -20,7 +21,7 @@
             android:layout_width="wrap_content"
             android:layout_height="20dp"
             android:layout_gravity="center_vertical"
-            android:src="@drawable/status_signature"
+            app:srcCompat="@drawable/status_signature"
             android:scaleType="fitCenter"
             android:tint="@color/light_black"
             />
@@ -144,4 +145,4 @@
 
     </LinearLayout>
 
-</LinearLayout>
\ No newline at end of file
+</LinearLayout>
diff --git a/app/ui/src/main/res/layout/recipient_alternate_item.xml b/app/ui/src/main/res/layout/recipient_alternate_item.xml
index 49c7876a8..d92e47fc1 100644
--- a/app/ui/src/main/res/layout/recipient_alternate_item.xml
+++ b/app/ui/src/main/res/layout/recipient_alternate_item.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
@@ -66,7 +67,7 @@
             android:padding="8dp"
             android:id="@+id/alternate_remove"
             android:background="?android:selectableItemBackground"
-            android:src="?attr/iconActionCancel"
+            app:srcCompat="?attr/iconActionCancel"
             />
 
     </LinearLayout>
@@ -118,7 +119,7 @@
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:layout_gravity="left|center_vertical"
-                android:src="@drawable/status_dots"
+                app:srcCompat="@drawable/status_dots"
                 android:tint="?attr/openpgp_grey"
                 />
 
@@ -139,7 +140,7 @@
             android:layout_gravity="center_vertical"
             android:layout_margin="13dp"
             android:id="@+id/alternate_crypto_status_simple"
-            android:src="@drawable/status_lock"
+            app:srcCompat="@drawable/status_lock"
             android:tint="?attr/openpgp_black"
             android:visibility="gone"
             tools:visibility="visible"
diff --git a/app/ui/src/main/res/layout/recipient_dropdown_item.xml b/app/ui/src/main/res/layout/recipient_dropdown_item.xml
index b4badedfe..b0a5a0d1a 100644
--- a/app/ui/src/main/res/layout/recipient_dropdown_item.xml
+++ b/app/ui/src/main/res/layout/recipient_dropdown_item.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
@@ -57,7 +58,7 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_gravity="left|center_vertical"
-            android:src="@drawable/status_dots"
+            app:srcCompat="@drawable/status_dots"
             android:tint="?attr/openpgp_grey"
             />
 
@@ -78,10 +79,10 @@
         android:layout_gravity="center_vertical"
         android:layout_margin="13dp"
         android:id="@+id/contact_crypto_status_icon_simple"
-        android:src="@drawable/status_lock"
+        app:srcCompat="@drawable/status_lock"
         android:tint="?attr/openpgp_black"
         android:visibility="gone"
         tools:visibility="visible"
         />
 
-</LinearLayout>
\ No newline at end of file
+</LinearLayout>
diff --git a/app/ui/src/main/res/layout/recipient_token_item.xml b/app/ui/src/main/res/layout/recipient_token_item.xml
index e93ea92b1..26f5838b9 100644
--- a/app/ui/src/main/res/layout/recipient_token_item.xml
+++ b/app/ui/src/main/res/layout/recipient_token_item.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:orientation="horizontal"
     android:layout_width="wrap_content"
@@ -36,7 +37,7 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:id="@+id/contact_crypto_status_icon_simple"
-            android:src="@drawable/ic_status_corner"
+            app:srcCompat="@drawable/ic_status_corner"
             android:visibility="gone"
             android:tint="?openpgp_black"
             tools:visibility="visible"
@@ -46,7 +47,7 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:id="@+id/contact_crypto_status_icon_simple_enabled"
-            android:src="@drawable/ic_status_corner"
+            app:srcCompat="@drawable/ic_status_corner"
             android:visibility="gone"
             android:tint="?openpgp_green"
             tools:visibility="visible"
@@ -56,7 +57,7 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:id="@+id/contact_crypto_status_icon_simple_error"
-            android:src="@drawable/ic_status_corner"
+            app:srcCompat="@drawable/ic_status_corner"
             android:visibility="gone"
             android:tint="?openpgp_red"
             tools:visibility="visible"
@@ -69,7 +70,7 @@
             android:layout_marginEnd="6dp"
             android:layout_gravity="center_vertical"
             android:id="@+id/contact_crypto_status_red"
-            android:src="@drawable/status_dots_1"
+            app:srcCompat="@drawable/status_dots_1"
             android:tint="?attr/openpgp_red"
             android:visibility="gone"
             />
@@ -81,7 +82,7 @@
             android:layout_marginEnd="6dp"
             android:layout_gravity="center_vertical"
             android:id="@+id/contact_crypto_status_orange"
-            android:src="@drawable/status_dots_2"
+            app:srcCompat="@drawable/status_dots_2"
             android:tint="?attr/openpgp_orange"
             android:visibility="gone"
             />
@@ -93,11 +94,11 @@
             android:layout_marginEnd="6dp"
             android:layout_gravity="center_vertical"
             android:id="@+id/contact_crypto_status_green"
-            android:src="@drawable/status_dots_3"
+            app:srcCompat="@drawable/status_dots_3"
             android:tint="?attr/openpgp_green"
             android:visibility="gone"
             />
 
     </LinearLayout>
 
-</LinearLayout>
\ No newline at end of file
+</LinearLayout>
diff --git a/app/ui/src/main/res/layout/settings_import_account_list_item.xml b/app/ui/src/main/res/layout/settings_import_account_list_item.xml
index 52bcf42bb..050e1c943 100644
--- a/app/ui/src/main/res/layout/settings_import_account_list_item.xml
+++ b/app/ui/src/main/res/layout/settings_import_account_list_item.xml
@@ -26,7 +26,7 @@
         android:layout_marginStart="16dp"
         android:contentDescription="@null"
         android:focusable="false"
-        android:src="?attr/iconSettingsImportStatus"
+        app:srcCompat="?attr/iconSettingsImportStatus"
         android:visibility="gone"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintStart_toStartOf="parent"
diff --git a/app/ui/src/main/res/layout/settings_import_general_list_item.xml b/app/ui/src/main/res/layout/settings_import_general_list_item.xml
index 66fefc6b5..4ea6f3183 100644
--- a/app/ui/src/main/res/layout/settings_import_general_list_item.xml
+++ b/app/ui/src/main/res/layout/settings_import_general_list_item.xml
@@ -25,7 +25,7 @@
         android:layout_marginStart="16dp"
         android:contentDescription="@null"
         android:focusable="false"
-        android:src="?attr/iconSettingsImportStatus"
+        app:srcCompat="?attr/iconSettingsImportStatus"
         android:visibility="gone"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintStart_toStartOf="parent"
diff --git a/app/ui/src/main/res/layout/status_indicator.xml b/app/ui/src/main/res/layout/status_indicator.xml
index 4b453f783..0f20f0746 100644
--- a/app/ui/src/main/res/layout/status_indicator.xml
+++ b/app/ui/src/main/res/layout/status_indicator.xml
@@ -1,10 +1,12 @@
 <?xml version="1.0" encoding="utf-8"?>
-<merge xmlns:android="http://schemas.android.com/apk/res/android">
+<merge
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
 
     <ImageView
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        android:src="@drawable/ic_chevron_right_black_24dp"
+        app:srcCompat="@drawable/ic_chevron_right_black_24dp"
         android:tint="@color/status_todo_chevron"
         />
 
@@ -17,15 +19,15 @@
     <ImageView
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        android:src="@drawable/ic_check_black_24dp"
+        app:srcCompat="@drawable/ic_check_black_24dp"
         android:tint="@color/status_ok_checkmark"
         />
 
     <ImageView
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        android:src="@drawable/ic_close_black_24dp"
+        app:srcCompat="@drawable/ic_close_black_24dp"
         android:tint="@color/status_error_cross"
         />
 
-</merge>
\ No newline at end of file
+</merge>
diff --git a/app/ui/src/main/res/layout/text_icon_list_item.xml b/app/ui/src/main/res/layout/text_icon_list_item.xml
index d6616bb6a..ae8460b9e 100644
--- a/app/ui/src/main/res/layout/text_icon_list_item.xml
+++ b/app/ui/src/main/res/layout/text_icon_list_item.xml
@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
@@ -17,7 +18,7 @@
         android:layout_height="40dp"
         android:contentDescription="@string/account_settings_action"
         android:padding="8dp"
-        android:src="?attr/iconActionSettings" />
+        app:srcCompat="?attr/iconActionSettings" />
 
     <TextView
         android:id="@+id/text"
diff --git a/app/ui/src/main/res/values/styles.xml b/app/ui/src/main/res/values/styles.xml
index 9c4abcc8a..16dd89046 100644
--- a/app/ui/src/main/res/values/styles.xml
+++ b/app/ui/src/main/res/values/styles.xml
@@ -18,17 +18,17 @@
     </style>
 
     <style name="PositiveBulletPoint">
-        <item name="android:src">@drawable/bullet_point_positive</item>
+        <item name="srcCompat">@drawable/bullet_point_positive</item>
         <item name="android:tint">?attr/tintColorBulletPointPositive</item>
     </style>
 
     <style name="NeutralBulletPoint">
-        <item name="android:src">@drawable/bullet_point_neutral</item>
+        <item name="srcCompat">@drawable/bullet_point_neutral</item>
         <item name="android:tint">?attr/tintColorBulletPointNeutral</item>
     </style>
 
     <style name="NegativeBulletPoint">
-        <item name="android:src">@drawable/bullet_point_negative</item>
+        <item name="srcCompat">@drawable/bullet_point_negative</item>
         <item name="android:tint">?attr/tintColorBulletPointNegative</item>
     </style>
 
diff --git a/app/ui/src/test/java/com/fsck/k9/fragment/MessageListAdapterTest.kt b/app/ui/src/test/java/com/fsck/k9/fragment/MessageListAdapterTest.kt
index 1f7ca204d..74ddeceb6 100644
--- a/app/ui/src/test/java/com/fsck/k9/fragment/MessageListAdapterTest.kt
+++ b/app/ui/src/test/java/com/fsck/k9/fragment/MessageListAdapterTest.kt
@@ -9,6 +9,7 @@ import android.view.View
 import android.widget.CheckBox
 import android.widget.LinearLayout
 import android.widget.TextView
+import androidx.appcompat.app.AppCompatActivity
 import androidx.core.view.isGone
 import androidx.core.view.isVisible
 import com.fsck.k9.Account
@@ -29,7 +30,7 @@ import org.junit.Assert.assertNull
 import org.junit.Assert.assertTrue
 import org.junit.Ignore
 import org.junit.Test
-import org.robolectric.RuntimeEnvironment
+import org.robolectric.Robolectric
 
 private const val SOME_ACCOUNT_UUID = "6b84207b-25de-4dab-97c3-953bbf03fec6"
 private const val FIRST_LINE_DEFAULT_FONT_SIZE = 18f
@@ -37,7 +38,8 @@ private const val SECOND_LINE_DEFAULT_FONT_SIZE = 14f
 private const val DATE_DEFAULT_FONT_SIZE = 14f
 
 class MessageListAdapterTest : RobolectricTest() {
-    val context: Context = ContextThemeWrapper(RuntimeEnvironment.application, R.style.Theme_K9_Light)
+    val activity = Robolectric.buildActivity(AppCompatActivity::class.java).create().get()
+    val context: Context = ContextThemeWrapper(activity, R.style.Theme_K9_Light)
 
     val contactsPictureLoader: ContactPictureLoader = mock()
     val listItemListener: MessageListItemActionListener = mock()