Active Directory Bind and Login on Webmail doesnt work

Hi - in my Axigen Lab i have several problems and havent find a solution:

-Server 2022, Domain joined, fully patched and firewall to axigen open (LAN)

-a special user is created to read active directoty and this seems to be working well

-Login on Webmail fails in several configurations

-i didnt find a working todo to fix this

Is anybody fit in this topic to help we?

Thanks and sorry for my rusty english!
Ralf