[Mailman-Users] emails from mailman rejected with error "reject=550 Relaying denied. IP name possibly forged"

[Abdullah Maskari]

So it seems that my problem is that my mailman server attempts to 
communicate with mailhost through mailhost's outward facing IP rather 
than through its internal network IP, I have added an entry for mailhost 
in the hosts file but sendmail still insists on communicating with 
mailhost through mailhost's external IP. I am not sure how to change 
this behaviour.

Abdullah
> From: pshute at nuw.org.au
> To: stephen at xemacs.org; al.maskari at hotmail.com
> CC: mailman-users at python.org
> Date: Mon, 28 Jul 2014 13:47:40 +1000
> Subject: RE: [Mailman-Users] emails from mailman rejected with error "reject=550 Relaying denied. IP name possibly forged"
> 
> 
>  Stephen J. Turnbull wrote:
> > It occurs to me that the DNS problem may be that your HELO 
> > hostname (in the SMTP transaction) doesn't match the reverse 
> > lookup for the IP observed in the TCP connection.  That 
> > should be easy to fix in the Sendmail configuration.
> 
> That sounds like something similar to what happened to us when someone decided they'd reconfigure our mail server to send from a different ip address than we receive mail on. 
> 
> We got away with it for a long time, but as more recipients installed spam filters (this was a few years ago), we began to see more bounces when we sent mail. Fixed by setting up reverse lookup for the sending address.
> 
> Peter Shute