Symptoms

An Incoming Mail Handler was established to create a new issue or add a comment to an existing issue. You've tested the mail handler, which yields No messages in mailbox. Despite verifying configuration settings, you suspect something is wrong because after a period of time, its evident that incoming emails never create new issues nor are there any new comments for existing issues.   

Diagnosis

Search JIRA logs for the following messages:

 Reporter (XXXXX@XXXXX) does not have permission to create an issue. Message rejected.

 If you're an Atlassian Cloud user, you'll need to reach out to Atlassian Support. Support Engineers have access to JIRA Cloud logs and will be able to verify whether you're running into this issue.

Cause

The reporter(s) in question does not have the Create Issue project permission. 

Resolution

Update the Create Issue permission and/or Project Roles for the project permission scheme in question, which is explained in more detail here.

Be sure, too, that the email messages sent to JIRA come from addresses associated with the relevant user account.