[Mailman-Users] Mailman working but not sending mail

[RobG]

For those following the saga... :)

My switch to our new server is proceeding well, but I've hit a snag that 
I'm not sure what to do about.

Basically, Mailman is accepting messages just fine.  They appear in the 
Archives.  The web interface works.  I can watch the maillog and see the 
messages come in.  I see this, for example:

Sep 24 22:33:07 lists postfix/local[2862]: 4B57425E070: 
to=<listname at awhatever.com>, relay=local, delay=1.6, 
delays=1.5/0/0/0.12, dsn=2.0.0, status=sent (delivered to command: 
/usr/lib/mailman/mail/mailman post listname)

But, it doesn't seem to be sending messages out.

What can I do to fix this?

Thanks!

Rob