When sending emails and a delivery failure occurs it gets written to the
Delivery message qualification table. You can update messages to have a
failure type Hard, so they will be ignored in the future because those
become quarantined. We are receiving new errors that are adding email to
the end of it, so instead of a Hard failure, the failure type in
Undefined. Here is an example message: 554 delivery error: dd Sorry,
your message to * cannot be delivered. This mailbox is disabled
(554.30). - z...