Problem

At times, you would observe that Jira Service Management has marked an email as read however when you view the Jira instance, you would notice that an issue has not been created.

Diagnosis

Diagnostic Steps

• Checking the  atlassian-jira-incoming-mail.log if you enabled debug mode would show that the email was processed.. 
• Check the  processing log found at Admin > Application > Email Request > Log page shows that Jira Service Management processed the email.
• Confirm that the email is meant to be successful processed(Emails with large attachments would fail)

Cause

There is no clear known causes, one possible cause is a timeout while Jira Service Management was creating the email.

Resolution

To fix the issue and have Jira Service Management reprocess the email, do the following:

Jira Service Management only reads emails from the inbox folder in your mail server.

• Go to your incoming mail server.
• Find the email that was marked as read.
• Select the email and mark it as unread (Reopen the email).
• After a minute, Jira Service Management email process should run and read the email.

In a scenario that you automatically move read email to a different folder, you would need to:

• Move the issue back to your inbox folder.
• Perform the same steps above to have the email reprocessed by Jira Service Management