Auto optimize too many connections

FAQ.md

@@ -1416,13 +1416,16 @@ consider switching to a modern provider which supports push messages (IMAP IDLE)
 If your device has an [AMOLED](https://en.wikipedia.org/wiki/AMOLED) screen,
 you can save battery usage while viewing messages by switching to the black theme.
 
-By default auto optimize in the receive settings is enabled,
-which will switch an account to periodically checking for new messages when the email server:
+If auto optimize in the receive settings is enabled,
+an account will automatically be switched to periodically checking for new messages when the email server:
 
 * Says '*Still here*' within 3 minutes
 * The email server does not support push messages
 * The keep-alive interval is lower than 12 minutes
 
+In addition, the trash and spam folders will be automatically set to checking for new messages
+after three successive [too many simultaneous connections](#user-content-faq23) errors.
+
 <br />
 
 <a name="faq40"></a>

app/src/main/java/eu/faircode/email/DaoFolder.java

@@ -326,6 +326,9 @@ public interface DaoFolder {
     @Query("UPDATE folder SET tbd = 1 WHERE id = :id")
     int setFolderTbd(long id);
 
+    @Query("UPDATE folder SET poll = :poll, poll_count = 1 WHERE id = :id")
+    int setFolderPoll(long id, boolean poll);
+
     @Query("UPDATE folder SET poll_count = :count WHERE id = :id")
     int setFolderPollCount(long id, int count);
 

app/src/main/java/eu/faircode/email/ServiceSynchronize.java

@@ -1578,6 +1578,21 @@ public class ServiceSynchronize extends ServiceBase implements SharedPreferences
                                         " last connected: " + new Date(account.last_connected));
                         if (errors >= FAST_ERROR_COUNT)
                             state.setBackoff(FAST_ERROR_BACKOFF * 60);
+
+                        boolean auto_optimize = prefs.getBoolean("auto_optimize", false);
+                        if (auto_optimize) {
+                            Throwable e = ex;
+                            while (e != null) {
+                                if (ConnectionHelper.isMaxConnections(e.getMessage())) {
+                                    for (String ft : new String[]{EntityFolder.TRASH, EntityFolder.JUNK}) {
+                                        EntityFolder f = db.folder().getFolderByType(account.id, ft);
+                                        if (f != null)
+                                            db.folder().setFolderPoll(f.id, true);
+                                    }
+                                }
+                                e = e.getCause();
+                            }
+                        }
                     }
 
                     // Report account connection error