Incoming email rejected by YunoHost

Support
,
5

Good news: the alias is working! The error has changed, which means the first issue is resolved.

Now, the new error is different:

553 5.7.1 <surfing@tommi.space>: Sender address rejected: not logged in

This happens because tommi.space is also a domain on your YunoHost server. When Proton Mail delivers an email from surfing@tommi.space to your server, Postfix sees the sender address belongs to a local domain but the connection is not authenticated — so it rejects it as a potential impersonation attempt.

This is caused by the reject_sender_login_mismatch directive in Postfix’s configuration.

You have two options:

  1. Quick test: try sending your test email from an address that is not on a domain hosted by your YunoHost (e.g. a Gmail address :face_vomiting:). That should go through fine and confirm the alias works.

  2. Permanent fix: if you actually need to receive emails sent from @tommi.space via Proton Mail, you can comment out reject_sender_login_mismatch in /etc/postfix/main.cf and reload Postfix (systemctl reload postfix). SPF, DKIM and DMARC already protect against sender spoofing, so the security impact is minimal. Note that YunoHost may restore this line on regen-conf postfix, so keep that in mind.

This exact issue was discussed and solved here: Question Postfix -- 553 5.7.1 ... : Sender address rejected: not logged in

2 Likes