I've spent a few days trying to diagnose this myself but I've not got anywhere, so I hope for some help from the forums.
My server has two IP addresses: 126.96.36.199 (the main eth0) 188.8.131.52 (eth0:1)
I noticed that one of the domains on the shared main IP (184.108.40.206) is not receiving inbound emails. I tested the site on the other IP and it's receiving emails as normal. . .
I ran the following in command line:
[root@en3 ~]# netstat -an | grep :25
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN
tcp 0 0 220.127.116.11:25 0.0.0.0:* LISTEN
As you can see, it's listening on the second IP but not the first. I have checked to make sure Postfic configuration is set to listen on all addresses and it is. I have also taken a screengrab of Server Processes screen in Postfix: http://lannait.com/serverprocesses.png
Something looks wrong with the above. Can anyone suggest what I need to do to get Postfic listening on the main IP?