Your GMail address has a near infinite number of variations!
Did you know that your GMail address can be extended?
It can be a fantastic way to uniquely identify which source that gave away your address to a spammer, but more importantly - it helps you to filter your mail!
Let's say my address is email@example.com and let's say that I want to sign up for a newsletter for something useful - like a site for Silly Walk GIFs,
If I signup for the newsletter with mymail+SillyWalks@gmail.com- that is not only perfectly legal and working, it also means that the mail that arrives, has mymail+SillyWalks@gmail.com in the To:
are all working, valid addresses which are uniquely identifiable by you. #gmail #tip
via +Patrick Graber