With Gmail you can add a plus to the end of your email address followed by a label I.E. [email protected]. This works the same as your regular email but you can use the plus label to filter or automatically delete mails. It's also useful when you don't trust a company to add the company name after the plus to see of they sell your email to third parties.
it is good to know, that these labels are totally unknown to those email address dealers/buyers, so that they cannot just automatically remove all +* local parts for those rare google domain emails no one knows about !!
If you give your email as [email protected] then it will still receive it at [email protected] but now you know who sold it if you start getting spam sent to it.