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

[Peter Shute]

 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