Groupwise error 503 cause was found by Teamworks Integration!!!
For Information for all!
The error 503 was not a bug for the new groupwise Client, the error come also by older Client.
The reason was the Integration of Teamworks 18.2.0 (customer without Enterprise-Messaging licence can't update for TW 18.2.1)
We have solve this Problem with mf Support and the admin console and take away the tw integration