Is it just me, or does it now take longer to Quit Mail? I hit cmd-Q, and the window vanishes almost instantly, but the Mail App itself hangs around for about 10 secs. In 10.2.4 this used to just snap shut - end of story.
Hrm.
Open up the activity viewer and watch what it is doing. I will catch it trying to synchronize stuff with my IMAP server just before it goes down. And if I made the mistake of jumping in or out of VPN in the meantime it will need to be killed with a force quit