A secret of gmail --- evolve one gmail account to unlimited (a huge number but actually it is limited) email address

1) For example: if your gmail account is "mygmailacc@gmail.com"

2) Than you send an email to either one of the following email address:
my.gmailacc@gmail.com
my.gmail.acc@gmail.com
MyGmailAcc@gmail.com
my.GmailAcc@gmail.com
MYGMAILACC@gmail.com

Your account mygmailacc@gmail.com will also receive this email.

Its to tell you that google ignore "." and the capitalization of the email address, so you can add "." to anywhere of the account and change any word to capital case, you will still receive the email. This let you make many different email address and the limited number is depending on your account name's length.