Loop detection

I had another situation where a message was looping forever, being 
repeatedly delivered from my server to itself, and causing a high load. 
  The problem is that the MX record looks like this:

conservation.com.       3600    IN      MX      1000 0.0.0.0.

I've previously encountered the same problem with other domains.  Since 
the message is coming from inside my network and has a local FROM 
address, it's accepted for relaying.  Then because of the MX record it 
gets "relayed" from the server to itself and queued for relaying again 
and again.

With qmail-smtpd, this wouldn't go on for long, because there's 
primitive loop detection, counting the number of "Received" and 
"Delivered-To" lines.  But qpsmtpd is missing that.

I've attached a plugin that duplicates the loop-checking in qmail-smtpd.

-- 
Keith C. Ivey <kcivey@cpcug.org>
Washington, DC

• Loop detection by Keith Ivey
• Re: Loop detection by Robin Bowes
• Re: Loop detection by Matt Sergeant