Mail error 504 5.7.4 Unrecognized authentication type

[Wurzelseppi]

solved it now
This one helped me with it:

SMTP connection problem, docker installation

If you use discourse_docker, try setting this in your app.yml: DISCOURSE_SMTP_AUTHENTICATION: login If you don’t use docker, try setting this in your discourse.conf: smtp_authentication = login By default, Discourse uses plain authentication (which is not what MS Exchange expects): https://github.com/discourse/discourse/blob/be3a5a56ccc284b352aa65080fc6b955f73cc72a/config/discourse_defaults.conf#L74