Mail-Answer without Jira-Key

[Thomas Griem]

In some of my projects I receive answer-mails from other systems. Unfortunately there is no Jira-Key in the subject. So every time I receive an answer, a new ticket will be created.

Is there a way to check the incoming mail-subject for specific content (f.e. a different non-jira-key at the end of the subject, numbers, a phrase...), compare with the content of a custom field and than let the system decide? no match = new ticket, match = comment