Running the latest public beta. Did a clean install when deciding to run it. I have "Organize by Conversation" turned on in the Mail "view" menu. In Yosemite and before, Mail would consider any emails with the same subject, a "conversation", and group them accordingly. I guess same subject alone is not technically a conversation, but was always useful when cleaning out my inbox to have all, say "Your receipt from Apple." emails grouped in this manner. Did El Cap change the criteria for organizing by conversation (maybe "smarter" but a bummer for me)? Otherwise I can't figure out why the emails aren't grouping as before.