How do I stop getting email everytime someone registers?

How do I stop getting email every time someone registers? I am using Akismet with 100% stoppage of spam comments, but suspicious “people” are registering more and more and my mailbox is being filled with (I suspect) bogus users.
So far these bogus registrants are (apparently) being stopped by Akismet from posting comments once they register, but how do I stop the emails from coming telling me that somebody has registered?
All I really care about getting via email is when a comment has been posted.