Need to reply to Auto-Generated email

How can I change Request Tracker configuration so it can reply to and Auto-Generated Email?

Getting the below message in log file when trying to reply to a message. This message was created by a ticketing system outside my organization.

whatever@whatever.domian was blacklisted for outbound mail on this transaction.

I have read a lot of the threads about Bugzilla but I do not see any fixes.

Thanks In advance