Dupe Checker

A dupe is a message with the same message-id that arrives for the second time.

This can happen due to multiple reasons:

• the spam sender has your mail address multiple times on his list and sends out spam with the same message-id
• you get messages from a mailing list with multiple accounts
• you changed your Outlook account settings and Outlooks thinks that it needs do download all messages again
• ...

The Dupe Checker has an expiration age for cleaning old message-ids.