certified:
> gives: Received: from www.first.com (unknown [nnn.nnn.nnn.nnn]) regardless
> if sent by first or second.
The RECEIVED line contains Postfix myhostname value, not the email
address. And you should have proper DNS so that www.first.com
resolves to the IP address, and the IP address resolves to
www.first.com. This is often part of a spam check.
The "-f u...@example.com" specifies among others the Return-Path
address, as well as the from= address in Postfix logs. This is also
the address in the MAIL FROM command in the SMTP protocol, which
is what remote hosts use for early spam blocks.
Wietse
