Mail Groups Unrelated Emails into Conversations

So this worked for me, unsure if all steps are required but since it worked this is what I did.

Go to View in the nav bar at the top, deselect 'Organise by Converstaion'

Now go to Preferences>Viewing and deselect 'Include related messages' (it's 3rd from the bottom)

Now all of your emails will be single emails, not ideal.

Return to View in the nav bar and select 'Organise by Conversation' again.

All of your previously unrelated emails that were clumped together should be separated and only relevant ones are linked.

Hope that helps.

Long shot, but something harmless to try:

Select mailbox and then use Rebuild from the Mailbox menu.

charlie

Yes lots of us are experiencing exactly the same problem since 'upgrading' to Yosemite. I also have emails that should be a part of a conversation not being grouped but displaying as singular emails. You need to send them feedback - the more that do - the more they will take notice:

http://www.apple.com/feedback/macosx.html

Try this; (again a longshot), uncheck the box to thread messages, save, then re-check the box. This may force a re-index.

Long time ago I deselected "Include related messages" but I am still having this problem.

I just now deselected all options under the View Conversations ... it looks like it will work (for me).

I started using Airmail today as a workaround for this very, very annoying Mail bug. It is on sale half price in the app store.

I spent several hours on the phone to support with this issue - 58 unrelated emails grouped - I was bumped up to a senior tech and after trying everything he could think of - rebuild - reinstall - he suggested they'd need engineering to look at it - 4 day wait and then who knows how long trying to fix it - realising I could not afford to spend any more time on this he suggested making PDF's of the emails then deleting the whole group.

I did this, even though this means looking up PDF's to refer to quotes from suppliers and request from clients!!

The issue persists with a whole new set of unrelated messages now grouped.

This is how I solved the issue : http://wp.me/4kqiM

Yeah I have absolutely the same issue. Any help with this would be greatly appreciated. The Apple Mail app becomes useless when random emails are grouped in conversations (totally random receipients and times of the emails that have nothing in comon)..

I'm having the same issue as mhutson and it's highly irritating. I deal with 30-40 different clients and over a 100 different suppliers and all my emails are mixed around and grouped into random conversations which makes it very difficult to organize my mailboxes. Does Apple even read these comments? Seems as this has been a problem since 2012 and there's nothing they are doing about it. They manufacture cheap low costs gadgets in China but manage somehow to sell their products for thousands of dollars making a huge profit but can't simply fix real issues that real people deal with. My business is suffering now with this glitch in their OS and I want answers.

FACK YOU APPLE!!! FIX THE FACKING PROBLEM!! YOUR OS X systems suck ARSE!!! They always have problems. Your products are FACKING CRAP now that Steve is gone. You put no real effort into quality anymore, you just rush crap out the door so you can make your millions!!!

Yes, my mac mail is lumping totally unrelated messages together and keeps doing it. AND IT PEESES ME OFF!!!!!!

Same issue here. Seems to have started recently. I currently have a Conversation with 54 emails comprised of more than a dozen different email subjects from 20 different people. Ugh.

I notice that they are all from/to people I regularly correspond with. No junk mail messages or unknown people in this group. So they are all important messages. When I search for one of them, the most recent message in this conversation appears, so at a glance that search result seems unrelated. At least now I know to dig deeper to find emails.

This is terribly broken. Hope Apple gets to this soon.

I just noticed this problem too. I know I've seen it before I upgraded to Yosemite but today for the first time I saw emails grouped together from different accounts with completely unrelated content and senders. This is kind of ridiculous on Apple's part. I don't know what algorithm they use for this, but since every message thread has a unique identifier, it seems kind of simple and obvious how to group them. It's not characteristic of Apple to make things more complicated than they need to be. I hope they address this problem in the next update.

Awesome. This actually solves the issue. In addition to the steps listed, I actually deleted Envelope Index. Thank you. This is really something that Apple must fix as it causes important messages to go missing when you delete converstations.