Issue Summary

When creating an Work Item from an incoming email, Jira intermittently reports a failure to create with the following message:
Your request could not be created. Please check the fields have been correctly filled in. We can't create this issue for you right now, it could be due to unsupported content you've entered into one or more of the issue fields.
 
This can occur when all fields have been filled in correctly and all content is supported - the error message reported is misleading.

Steps to Reproduce

1. Send an valid work item creation email to the JSM incoming mail handler

Expected Results

The work item is created successfully

Actual Results

The work item creation fails and reports the following error:

Your request could not be created. Please check the fields have been correctly filled in. We can't create this issue for you right now, it could be due to unsupported content you've entered into one or more of the issue fields. 

Workaround

Currently there is no known workaround for this behavior - but this problem is intermittent and transient, the work item will get created if the email is resent.
For email sent to custom email requests, set the email back to "Unread" mode for it to be reprocess.