When I set up my server I named it server.domain.com not realising that my old server was named the same. I then went to change all instances that I was aware of from server.domain.com to server1.domain.com, but when I look at mail headers I see:
Received: by server1.domain.com (Postfix)
id 9322C1337425; Fri, 19 Aug 2011 18:47:50 +0200 (SAST)
Date: Fri, 19 Aug 2011 18:47:50 +0200 (SAST)
From: MAILER-DAEMON@server.domain.com (Mail Delivery System)
I have no idea where the From: ... picks up the server name.
Any direction to start looking would be great.