There is a new behavior with mail.app in Mountain Lion where if you have messages with the same title but in different folders (like trash, or archive) they show up in the threaded view. Say I get an email titled "new message from customer" and I want to keep it. I move it to Archive. Say I get another email "new message from customer", and I don't want it so I move it to trash. If I get a third email "new message from customer" in my inbox, if I view the email and scroll to the bottom of it, I can see the other 2 emails as if they were part of a conversation thread, though they are not. The Lion mail.app didn't do this. It only threaded emails with the same subject if they were in the same folder. In Mountain Lion, mail.app looks through all the folders and shows any email from any folder as part of a thread in your inbox. This is very annoying. If I file something away, I don't want to constantly see it referenced as if it was a thread. Is there a way to turn this off? ---------- I just found "hide related messages" but if I click it, it works but then as soon as I click off the email and click it again, the related messages show right back up. How do I permanently hide related messages?