Hum, on top of my head I’d say a resignation is not “effective” until it has been formally accepted. So you should perform your function until it has indeed been confirmed. But then, I’ve been out of school for ages and was in the military, so my “definitions” might be off a bit. Go with your gut feeling, if you feel there is a need for confirmation, then go for it. Makes you look better too, if you see it through instead of “e-mail -> gone”