Email appended to issue without JSD issue number in subject line

[Romy Meyers]

A customer sent an email to one of our JSD projects email channel and the email was actually attached (appended) to another issue but the email or subject did not contain the issue number anywhere and the subject of the emails differed somewhat. Has anyone else had this issue?! 

[Andrew Laden]

Jira can also look at email headers, in particular the "In-Reply-to" or the "References" headers.

These are also the same headers that most clients use for email threading. 

So odds are the email was a reply of an email that had previously generated a jira ticket, so the mail was appended to the same ticket.