notification for test date, by email or snail mail

I booked my test online about 2 weeks ago.

does anyone know if they send a letter out or send an email?

they say about 4 weeks before the test date, however my snail mail address is really unreliable. sometimes we never get post correctly, so i avoid regular mail contact.

if they send the notification by email then it's fine, I'll just wait. if they send by regular mail it may have been misplaced/lost or at the wrong house.