Issue

When a Jira Core Mail handler (configured in ⚙ > System > Incoming Mail) is setup with a Service Desk Project and with the "Create users" option enabled, the creation of new users from email will fail if no default application access it set in the Jira instance.

The following error will be thrown in the Jira Incoming Mail Logs:

2019-10-14 10:41:01,067 DEBUG [XXXXXX] Caesium-1-4 anonymous  XXXXX Cannot find reporter for message. Creating new user.
2019-10-14 10:41:01,067 ERROR [XXXXXX] Caesium-1-4 anonymous  XXXXX[10100]: There are no default applications configured, new users are not assigned to any groups therefore they can not create issues. Please visit Application Access page for more information.

The behavior is intended by default, since the Jira Core Mail Handler is not designed to be used with a Service Desk project, as it expects users to have application access to create emails (but Service Desk customers are by design users without application access).

Due to the fact that the Jira Core Mail Handler contains more configuration and features than the Service Desk Mail Handler (configured in Project Settings > Email Requests), some customers prefer to use the Jira Core Mail Handler rather than the Service Desk Mail Handler.

Suggestion

Add some configuration to the Jira Core Mail Handler to allow the creation of customer-type users (users without application access), when it's configured with a Service Desk project and when no default application access is configured.