My website sends emails to me with the same subject and they are being grouped into conversations even if I delete old ones (Mail, Gmail). I know I can change the subject to prevent this, but is there a header or something else that can be added to do this without forcing unique subject lines?
On the top of my head, there are two methods to avoid threading:
- set the SMTP header
X-Entity-Ref-IDwith any value. This is what Google+ notifications do. - change the sender email (you can use
From: info+randomstring@example.com). This is what Facebook notifications do.
The threading will be made if you force it with Reference or Reply-To.
Gmail has changed the game - check out this article - https://gsuiteupdates.googleblog.com/2019/03/threading-changes-in-gmail-conversation-view.html - as a result, your system generated emails are probably no longer threading if your situation is like mine. Good for you, but that wasn't what I wanted for my use case! Enjoy.
来源：https://stackoverflow.com/questions/23434110/force-emails-not-to-be-grouped-into-conversations