Queue is full of messages from MAILER-DAEMON to non-existent domains
-Messaging Gateway version 10.0.1
When I view the Messaging Queue in our gateway it is full of messages To email addresses of domains that don't seem to exist and they're From MAILER-DAEMON. The error is 421 4.4.0 [internal] Failed to connect: no mail servers for this domain could be reached at this time.
When I search the Audit Logs for the recipient address, it indicates that it was marked as spam.
What is causing these messages to fill up the queue.
P.S. If needed I can provide a snapshot of the Messaging Queue and/or Audit Logs.