iOS 6 Mail sent sound plays before mail is sent. :-(
I'm not sure whether it's a bug or a feature, but iOS 6 changed when the "swoosh" sound is played from being when the mail is actually sent to when you hit "Send."
You can see this by sending email from the device; you'll hear the "swoosh" long before the "Sending" progress bar has completed.
This somehow doesn't seem like the right thing to do…
Mac Pro, OS X Mountain Lion