i recently added an new domain containing a german umlaut (ä) to my mailcow mailserver.
The mailcow UI translated the domain to the matching punycode domain, which is as far as i know correct.
If i try to login into SoGo i have to use the punycode domain which is pretty ugly (Nothing new for me. Read about this)
Apparently all other email clients aren’t able to login with the corrent looking domain name either.
The postfix log is showing the following error
warning: ip-xxx-xxx-xxx-xxx.hsi05.unitymediagroup.de[xxx.xxx.xxx.xxx]: SASL LOGIN authentication failed: VXNlcm5hbWU6
Is there a propper way to use these kind of domains with mailcow or even any other mail server system?