Possible mutations of a Gmail email address

The Blog Senseful Solutions has a good article on How Gmail Filter Email-Matching Works.

To quote them:

The default account you use (e.g. john.smith@gmail.com) will match all variations of your address. This includes dot notation, plus addressing, and using the googlemail.com domain.

Here’s a brief explanation of each:

• Using dot notation: You can enter as many non-consecutive dots in your email as you want. For example, if your email is john.smith@gmail.com, mail sent to j.o.h.n.s.mith@gmail.com will still arrive at your account.
• Using plus addressing: After your account name, you can enter the + sign and whatever text you want afterwards followed by the Gmail domain. For example, mail sent to john.smith+foo@gmail.com will arrive at john.smith@gmail.com.
• Using googlemail.com domain: Any mail sent to your @googlemail.com will arrive at your @gmail.com address. For example, mail sent to john.smith@googlemail.com will arrive at john.smith@gmail.com.

Any of the above can be combined (e.g. j.o.h.n.s.m.i.t.h+foo.bar@googlemail.com will still go to john.smith@gmail.com).