Setup Secondary Mail Relay

[kilburn]

It was my fault, not yours. You are missing a proper "relay_domains" map, something like:

/etc/postfix/main.cf

Code:

...
relay_domains = hash:/etc/postfix/relay_domains
...

/etc/postfix/relay_domains

Code:

domain1.tld       OK
domain2.tld       OK
...

Remember to postmap the relay_domains file and reload postfix config. This way postfix will relay things about these domains but not about any others