Hello, I recently had to disable duplicate suppression on our mailservers as a broken mail client (=some Outlook versions) reuses the message-id if you forward a message.
Long story short, the users are now complaining about duplicated emails instead of never received messages... Here's my proposal to make duplicate suppression more robust: Combine the "message-id" header field with the "date" header field for the duplicate check. If a broken client reuses the message-id, there's a good chance the date field changed. Opinions? Best regards, Thomas Jarosch
