Diagnose no inbound mail handled
What needs to be done when there are no inbound mail being handled by JEMH but do reside on the mail server.
JEMH Auditing
The very first thing JEMH does when a mail is processed by JEMH is creates a Audit record which resides under Auditing screen in JEMH (do ensure the Auditing is enabled). This process is dealt at the very beginning before performing any other functionality. Important: if the expected mail is not showing in the Auditing screen, it would mean that JEMH has not processed the mail.
How to get the Processing/Report Details of a processed mail
JEMH v2.7 or below
Navigate over to JEMH > Auditing
Once in Auditing, scroll down to the bottom and you'll see a list of emails that were processed by JEMH
Once the corresponding mail has been found, select Processing Detail
Once clicked, JEMH will navigate you to the Processing Detail page
JEMH V3.0 or above
Navigate over to JEMH > Auditing
Once in Auditing, select Incoming Mail side menu which will expose all the Inbound Mails handled by JEMH
Click on Report for the corresponding mail and this should open a new dialogue with the Report information
In some cases, you might want to create a Test Case out of the mail, this can done by clicking the More (...) option and selecting Create Test Case. If you now go over to Test Cases, you'll notice a new test case
Inbound Mail Server connection
It's recommended to double check if the Inbound Mail Server is passing the validation tests. This can be done by editing into the corresponding POP/IMAP Mail Servers (Jira > Settings > System) and click on the Test Connection. This will ensure the connectivity to the Mail Server which can be impacted by changing credentials, changing Timeout (might be set to something short which doesn't provide enough time to connect to the server).
Mail Handler section
The purpose of a Mail Handler is to configure Jira to handle the mails which are to be coming in via the Inbound Mail Server. Here, you can set up a JEMH Mail Handler against an Inbound Mail Server. You must ensure the relationship between the Mail Handler and Inbound Mail Server is one to one. This means that a single Inbound Mail Server should not have multiple Mail Handlers set up against it as this will not provide a consistency of which Mail Handler is dealing with which mail.
Inbound Mail and Black Belt logging
Last resort is to check the logging. This can be implemented by following the instructions provided by Atlassian on Diagnosing Mail and Mail Handlers Issues.