OS X 10.11 Beta 2 - Mail still don't works

No, it works

You could try turning off all your email accounts in System Preferences and see if it works. If it does, it should be easy to isolate which account is causing it.

If it doesn't then the simplest thing to do might be a clean reinstall.

You could also try deleting com.apple.mail and rebuilding by setting accounts up fresh in the app. That worked for me back in the Yosemite dev betas

I should state that this carries much less risk assuming you are using IMAP accounts of course 🙂

I had this problem and fixed it by rebuilding my spotlight database. ie mdutil -E /