OSEC

Neohapsis is currently accepting applications for employment. For more information, please visit our website www.neohapsis.com or email hr@neohapsis.com
 
Re: 4xx SMTP Messages and Backup MX Usage

From: Wietse Venema (wietseporcupine.org)
Date: Sat Oct 23 2004 - 13:48:43 CDT


Matt Jeanneret:
> Hello,
>
> I am attempting to send email to a domain that has two MX records. I am
> using Postfix 2.1.5. The primary MX host responds with a "421 SMTP
> service not available, closing transmission channel" and the secondary
> MX host is never attempted. The message stays in the queue until it is
> bounced back to the sender.

You did not tell us that Postfix gives up after TWO attempts. The
primary for fedex.com has two IP addresses.

Sites that list a primary that never accepts mail should fire their
IT staff.

        Wietse

smtp_mx_session_limit (default: 2)
       The maximal number of SMTP sessions per delivery request
       before giving up or delivering to a fall-back relay host,
       or zero (no limit). This restriction ignores IP addresses
       that fail to complete the SMTP initial handshake.

       This feature is available in Postfix 2.1 and later.