Force emails not to be grouped into conversations

Question

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?

Answer 1

On the top of my head, there are two methods to avoid threading:

• set the SMTP header X-Entity-Ref-ID with any value. This is what Google+ notifications do.
• change the sender email (you can use From: [email protected]). This is what Facebook notifications do.

The threading will be made if you force it with Reference or Reply-To.