GMail Plus Addressing is a very useful trick to save your mailbox from spam. And if you get spammed, you know exactly which website / online service leaked your email address to spammers.

What is GMail Plus addressing? Say you have an email address like billgates@gmail.com. If you append a "plus" sign to your email username, gmail will ignore anything written between the + and @ sign.

So any email address sent to billgates+microsoft@gmail.com or billgates+blog@gmail.com or billgates+website@gmail.com will still reach your billgates@gmail.com inbox though technically, they are three different email aliases.

When you share your email with some non familiar service, like a newsletter, you can supply your existing email with a plus sign. If you ever receive spam addressed to that email alias, you know the exact source that's sending the spam and can easily block all emails using a GMail filter.

[type the alias in the To: fiedd and redirect all incoming message to Trash or apply a new label]

More GMail Easter Eggs [including the dot trick].