GMX IMAP synchronisation fails

Hello,
I struggle to configure my GMX account. CalDAV and contacts are fine.
I started the configuration with my standard password.
The initialization failed and asked for a password. I entered the first application specific password and the eM Client could send and receive a test mail.
After this, I entered a second application specific password in IMAP configuration page.
Now, eM Client fails to synchronize.
Here the protocol:

21:02:36 GMX <*****>@gmx.de [IMAP] MailClient.Accounts.ConnectionException: Die Synchronisation des Ordners'GMX <*****>@gmx.de/Posteingang' ist fehlgeschlagen mit folgendem Fehler: Der Server hat nicht innerhalb von 00:01:00 geantwortet
          ---> System.TimeoutException: Der Server hat nicht innerhalb von 00:01:00 geantwortet
            at MailClient.Imap.Base.Extensions.CopyToAsyncWithTimer(Stream source, PipeWriter writer, TimeoutTimer timer, IProgress`1 bytesRead, Action`1 loggingCallback, CancellationToken cancellationToken)
            at MailClient.Imap.Base.TransportPipe.StartReading(Stream stream, CancellationToken token)
            at System.IO.Pipelines.Pipe.GetReadAsyncResult()
            at System.IO.Pipelines.Pipe.DefaultPipeReader.GetResult(Int16 token)
            at MailClient.Imap.Base.Extensions.<ReadLineAsync>g__SlowAsyncPath|30_1(PipeReader reader, CancellationToken cancellationToken)
            at MailClient.Imap.Base.Connection.ReceiveAsync()
            --- End of inner exception stack trace ---
            at MailClient.Protocols.Imap.ImapActionCommand.ExecuteInternalSync(WorkerStatus status)
            at MailClient.Protocols.Imap.ImapActionCommand.Execute(WorkerStatus status)
            at MailClient.Commands.Command.Process(WorkerStatus status)
         --- End of stack trace from previous location ---
            at MailClient.Protocols.Imap.ImapAccount.SynchronizeIntAsync(Boolean forced)
            at MailClient.Protocols.Common.SynchronizableMailAccount.<>c__DisplayClass22_0.<<SynchronizeAsync>b__0>d.MoveNext()
           AccountId = <*****>-<*****>-<*****>-<*****>-<*****>
           AccountName = GMX <*****>@gmx.de
           IMAP_SERVER_TYPE = Gmx
           RunInPlace = False
           GUIStatus_Exception_Reported = True

Please, help.
Thanks.
Uli3

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