Version 10 SMTP issue with t-online

Hello,
after upgrading from eM Client 9 to version 10.0.3266 (7060eea) I have the problem that SMTP access to my t-online account no longer works.
When syncing, the message “The SMTP server does not support authentication.” appears.

In the account settings, I have entered the settings recommended by t-online
Server: securesmtp.t-online.de
Port 465
Security: Use SSL/TLS on specific port (legacy)

The repair function always reports “Repair failed”
Even a new app password within t-online was not successful.

Does anyone have an idea how to fix the problem?

Thanks and Regards
emr

Port 587
SSL/TLS erzwingen