A mail queue attempts to resend items up to 10 times. If the operation fails for the 11th time, the items are put into an error mail queue.
You can remove items from the error mail queue in one of the following ways:
  - Manually clear the whole error queue.
  - Manually resend all items from the error queue to a mail queue.
You should pay attention to the cases where an error mail queue item gets back to an error mail queue after you resend the items manually. These cases might indicate permanent performance issues.