If you use Mail.app on OS X Mavericks, there’s a good chance you already know this, but if not: Apple have just updated it.
Much has been made of Gmail not working under Mail.app on Mavericks, but for those of us who use it with Exchange, it’s been a similar story (with less rage). I’m happy to report that the latency/timeout/crash problems I was experiencing with Mail.app and Exchange 2010 appear to be resolved with this update.
And there was much rejoicing!