WHM brings up this message:
This message was created automatically by mail delivery software. A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed: [email protected] (ultimately generated from [email protected]) Domain example2.com has exceeded the max defers and failures per hour (1000/1000 (92%)) allowed. Message discarded.
There is a special place somewhere on the disk where you can lift this hold. Probably in /etc somewhere.