remoteStore assocciated with account indirectly should also be reseted when acccount was removed. Otherwise, there might be residual data that will affec account being added later.

src/com/fsck/k9/Preferences.java

@@ -123,6 +123,14 @@ public class Preferences {
             accountsInOrder.remove(account);
         }
 
+        try {
+            account.getRemoteStore().resetRemoteStore(account);
+        } catch (MessagingException e) {
+            Log.e(K9.LOG_TAG, "Failed to reset remote store for account "
+                    + account.getUuid());
+            e.printStackTrace();
+        }
+
         account.delete(this);
 
         if (newAccount == account) {

src/com/fsck/k9/mail/Store.java

@@ -209,5 +209,13 @@ public abstract class Store {
         return mAccount;
     }
 
+    public void resetRemoteStore(Account account) {
+        String uri = account.getStoreUri();
+        if (uri.startsWith("local")) {
+            throw new RuntimeException(
+                    "Asked to get non-local Store object but given LocalStore URI");
+        }
+        sStores.remove(uri);
+    }
 
 }