[Mailman-Users] "sender domain must resolve" errors

[Bob Puff@NLE]

Hello,

I've noticed that I'm seeing a lot of "Sender domain must resolve" messages
in my Postfix logs, most of which are from messages sent thru Mailman.  I know
this isn't specifically a mailman issue, as the errors are coming from the
other SMTP servers, but perhaps someone here can help shed light on this.

Here's some of the errors from my log:

         5   host smtp1.cei.net[204.117.117.29] said: 451 4.1.8 <apostles-today-admin at apostles-today.net>... Sender domain must resolve
         5   host edify-ministries.org[209.190.211.167] said: 451 <apostles-today-admin at apostles-today.net>... Sender domain must resolve
         5   host mail.hiwaay.net[208.147.154.56] said: 451 4.1.8 <bwade at hiwaay.net>... Domain of sender address apostles-today-admin at apostles-today.net does not resolve
         5   host mail.odyssey.on.ca[209.213.224.2] said: 451 4.1.8 <apostles-today-admin at apostles-today.net>... Domain of sender address apostles-today-admin at apostles-today.net does not resolve
  
Note that apostles-today.net resolves nicely to an IP address.  This is a
virtual host on a shared IP, so a reverse IP lookup obviously isn't 
going to show the 50 or so addresses on that IP.  Is there something else I'm missing?

Bob