If email processing stops before its delivery result is saved, the message is now flagged for checking. An uncertain message is not automatically sent again.
Ordinary failed deliveries continue to use their scheduled retry checks.
Delivery outcomes are checked separately
If email processing is interrupted and no final delivery result has been saved, the message is held for checking after its processing window expires. It is not automatically sent again when delivery may already have occurred.
This helps prevent repeat emails after interrupted processing. It does not prove whether an individual recipient received a message, and a message held for checking may be delayed. Ordinary failed deliveries with a known result retain their retry behaviour.