|Your email will have looked a little like this.|
I was going to write a post showing how to block this person from following you but after clicking through to their link it gives a page 404 error. Basically that tells me that their account has been deleted, most likely as a result of them going on a mass following spree which has been interpreted (correctly) as spam.
|Spammers gotta spam.|
Just go to your profile, click followers, find the follower and click the X next to their name and click OK when it asks for confirmation.