Mailcow times out on own Postfix

dahe22

I added a new domain relay.com which uses the option Relay this domain and Relay all recipients.
Everything received should be relayed, so I created a Transport Map with destination .*relay\.com and the Next hop of another Postfix server.

When sending an E-Mail to eg. test@relay.com i get following error in the Mailcow Postfix Logs:
27DF9EAAC8: to=<test@relay.com>, relay=none, delay=61, delays=1/0.02/60/0, dsn=4.4.1, status=deferred (connect to hostname-of-mailcow.example.com[1.2.3.4]:25: Connection timed out)

Happy about any ideas. Thanks!

pkernstock

Based on the error Connection timed out of outgoing TCP/25 connections, I’d assume your ISP is blocking outgoing traffic on TCP/25. You might want to double-check with your ISP.

dahe22

@pkernstock
Thanks for your Input!
Funny thing is the Postfix log of Mailcow essentially says it can not reach itself.
Outgoing Port 25 is allowed, but shouldn’t make any difference since telnet 1.2.3.4 25 works. Traceroute proofs that 1.2.3.4 is 1 hop away.

Forgot the most important information: This Set-Up worked till I configured the “other postfix” to relay the Mails back to postcow through relayhost option.
May seem like a really strange setup to relay from postcow to another postfix and then back to postcow. But “other postfix” has no Spam protection and shouldn’t be reachable from the internet over port 25 and does recipient rewriting.

dahe22

Solved by changing the MX Record to “other postfix” and removing the corresponding Domain and Transport Map from postcow.
It seems like the two components (relay to other postfix, relay back to postcow) worked on it’s own but not combined.

I am pretty sure it’s didn’t loop, since “other postfix” changed the recipient so it didn’t get relayed back.