Strange one this. I have a quite a few domains and mailboxes and all of it works except one email domain where I have a few mailboxes and none of them can have mail delivered. I get an undelivered mail message. Code: Final-Recipient: rfc822; [email protected] Original-Recipient: rfc822;[email protected] Action: failed Status: 5.1.1 Diagnostic-Code: X-Postfix; unknown user: "admin" However, the mailbox [email protected] works and I can see current email in it (configured in thunderbird). I wonder if it's a routing / hostname issue as the xavserver.co.uk is the hostname of the server running ispconfig.
You must have listed xavserver.co.uk somewhere in /etc/postfix/main.cf or /etc/mailname. Remove it from there and restart postfix. Both files may only contain the server hostname, e.g. server1.xavserver.co.uk but not the domain itself. If you have the domain there, then it gets disabled for email receiving.
Thank you Till! I had the hostname listed in main.cf. I've removed it, leaving just localhost and it appears to be OK now.
In fact, I think this is down to me: when I built the server following the guide, I remember seeing something like you have to use "server1.example.com" and not just "example.com". I don't think it said why, but this would be the reason (there are probably more). However, my server's FQDN is xavserver.co.uk, I don't have it as a subdomain or other server, so wasn't sure whether not having a "fake" subdomain would be a problem. Clearly, you have to make a fake entry because the truthful hostname when a domain name, is an issue for postfix. I'll try to remember that next time I rebuild the server
A fake entry is not good as well as other servers will try to verify it. Just add the server hostname, which should be a subdomain of your domain, no matter if you use server1.yourdomain.tld, mail.yourdomain.tld or whatever as an A-Record in DNS which points to your server IP. Then the mail system should work.
