I've restarted the server and attepted a login with everything prefilled so only the login attempt is logged.
Here are the messages from this attempt: https://pastebin.com/hejRQBji
There is no mail.err

If there are any other logs I can provide that I totally missed please tell me.

On 19/07/2020 22:46, Alexander Dalloz wrote:

Am 19.07.2020 um 22:08 schrieb Nils:

> I still see "warning: dict_nis_init: NIS domain name not set - NIS lookups disabled" in your pasted logs.
It's only there bc this logs are made before I made the change in config regarding this.
Can't find it in any newer entries after restarting postfix.

Then please provide current log content. Not the old one with the MUA's autoconfig using pipelining. It is important to see the failure track when you try to send a mail through port 587.

Alexander