Mail "Organize by Conversation", grouping rule is changed?

Same issue here, after updating to El Capitan, this feature doesn't work anymore. Apparently just sent emails are organized. Any advice?

Same here, I reported this problem during beta testing, but El Capitan was released with this bug... Mac OS X Mail client unusable for me right now... Seems to work only on iCloud inbox... Thinking about going back in Time (Machine) ...

****, same here. Very annoying.

Same here. Mail no longer groups emails by conversation.

Any updates?

I'm in agreement that this feature from Yosemite needs to be reinstituted in El Capitan.

I have not figured out the rules yet. Some of my emails are combined and some are not. Definitely much fewer than under Yosemite though. I would like to see it put back the way it was.

Same here. I'd just like to bump this so we can get a solution.

I receive automated emails from my kids' daycare each day. Obviously by now I have hundreds of them. They used to be grouped nicely on the left-hand panel with a little number (say, 142) that could then be scrolled through on the right-hand panel. Now, each email from them is listed separately on the left, clogging my inbox.

The older system was far better.

It seems that they are now only grouping emails that have "Re:" in the subject and not just the same subject. I've run some tests and emails with "Re:" get grouped and those with just the same subject do not.

I have not tried all perturbations of email but I have exchanged email between two accounts and with the same subject but no "Re:" there is no grouping, same subject with "Re:" and they get grouped. Try it yourself.

Messages from this forum do get grouped without the "Re:" but there is some other method involved. Probably an email header that Apple uses because it wrote Apple Mail to recognize it.

Same issue here. Any way to revert it back to how it was working in Yosemite?

I will try to pull out Mail.app from Time Machine Yosemite backup and let you guys know what happened ...

...that was fast, crashing on start, still looking for another solution... 😟

I experimented with this a bit - the "organized by conversation" appears to be "organize by 'references' AND 'subject' using the logical "AND" operator meaning both fields have to be equal and then the messages are grouped together.

"References" appear to be unique ID numbers created for each message and appended to the previous referenced (replied to?) messages for each thread.

You can see the list of referenced messages on a grouping by pressing "cmd-shift-h" or "view, message, headers" when a message is selected.

I liked the old way myself - I have an automated hourly e-mail sent (from a weather station) that I liked having grouped together...

Definitely annoying that they have removed this feature. I'm trying to find where to report it as a bug, but it seems like I need to be a developer to put through bugs. Do you think it's a bug or a feature change?