On Wed, 11 Apr 2012 09:37:28 -0500 Scott Nelson <sbnelson at thermeon.com> wrote: > We receive messages from a system that sends e-mails with a blank > Reply-To: and CC: lines, and (I think) mimedefang is rejecting them. That rejection message is not part of stock MIMEDefang. What's your filter doing? Regards, David.