Service Desk incoming mail handlers have pre-configured rules that prevent them from processing automatically generated messages (e.g. auto-responses or delivery status bounces), to avoid mail loops.

For example, email messages with an empty Return-path tag in the header aren't picked up. In the handler log (JIRA Admin > Add-ons > JIRA Service Desk - Email settings > View log), an error message is displayed:

The message was rejected because it has delivery status.

This isn't quite clear and should be reworded, to e.g. The message was rejected because it is an automated delivery status message.