Summary

When the mail puller encounters an message in the mail channel mailbox originating from an invalid formatted "From" field, the mail puller will not be able to process that message, and continuously loop on this message, effectively rendering the mail pulling process broken. A correctly formatted looks like "name@domain.extension".
A known source for this issue is Microsoft Outlook 365, where certain messages originate from "Microsoft Outlook" opposed to a valid email address in the "From" field.

Steps to Reproduce

1. Ensure the mailbox configured as mail channel in a Service Desk project contains an email originating from a source which does not provide a valid formatted email address in the "From" field as described in the summary
2. Have the mail puller pull and process the email automatically

Expected Results

The mail gets pulled into the database.
In this case, it is not relevant for the email to get processed further beyond this point.
Once the email has been pulled, the mail puller should continue to pull mails from the mail box.

Actual Results

The mail puller gets stuck on the incorrect email and will continuously loop on it, instead of moving on to the next mail in the mailbox.
The atlassian-jira-incoming-mail.log file will display the following error for each attempt to pull the mail in question:

Unable to create issue with message.
javax.mail.internet.AddressException: Local address contains control or whitespace in string ``Microsoft Outlook''

Notes

The relevant message in Microsoft Outlook is an automatically generated one to inform the user of certain changes on the mail platform, or the welcoming message when starting to use the product for the first time. So far, no other mail providers are known to cause similar issues.

Workaround

Delete the offending message from the mail box. This will allow the mail puller to proceed from that point onwards.