IMAP Account with Kopano Mail Server Error at save


i have some trouble to get an incoming imap account working.

the problem is, that if i configure the account and add a password and remove the flag from “awaiting_password” i get an 499 from nginx (browser 502 error code) and i am not able to save the password from my account.
If i tick the checkbox awaiting_password ( so that it is marked) , then i am able to save the imap account.

Unfortunatly i have no error logs under /frappe-bench/logs, also no logs in the browser developer console.

i am able to send mails via smtp through my account (so the domain settings are working)


centOs 8
bench 4.1.0
frappe and erpnext developer
Python 3.6.8