Help with Mail Loop Issue in Mailcow Outgoing Mail Setup
Hello,
I’m setting up a Mailcow domain with an outgoing mail server. Here’s what I’ve done so far:
Added the domain:
Went to Admin > System > Routing, added a relay domain on my relay server, and created a routing rule with the transport set to the configured domain.
After testing, outgoing emails are sent successfully and reach their destination. However, when the recipient replies, the message arrives at the relay server, which then routes it back to Mailcow, creating a loop.
Here’s the error from the logs on relay:
2025-07-21T14:24:03+00:00 localhost postfix-mailcow[3676257]: Jul 21 10:24:03 41e02873da0a postfix/smtp[382]: 18096202063: to=henrik@mydomain.net, relay=192.168.10.11[192.168.10.11]:25, delay=0.3, delays=0.04/0/0.14/0.12, dsn=5.4.0, status=bounced (host 192.168.10.11[192.168.10.11] said: 554 5.4.0 Error: too many hops (in reply to end of DATA command))
I tried removing the routing rule and adding relayhost = 192.168.10.11 to the extra.conf, but the issue persists.
I can see the initial error message, but I’m not sure how to resolve the loop. Any suggestions would be greatly appreciated!
Thanks in advance.