Mail service should ignore obvious mail bounces

JIRA's mail service (which processes incoming mails) should have the ability to ignore mail bounces, so that they do not result in new issues (and possible mail loops).

Of the jira-user bounces I receive:

• 75% have a Content-Type: multipart/report header
• 17% are from *mailer-daemon@'
• 8% are from majordomo, and the subject starts with "BOUNCE" (most people wouldn't get these).

Of bounces to personal mail, almost 100% are covered by the first two of these heuristics.

Almost none of these bounces have the Precedence: bulk header, which we added a check for in an attempt to avoid bounces.

So without going overboard and implementing a full mail filter in JIRA, I think we could identify most mail bounces with 2 simple hardcoded rules.