One of the most popular ways of dealing with the deluge of spam that people receive is to have two e-mail accounts. One e-mail account is used for private correspondence, and the other is used for giving out to websites etc. The thinking is that if this address ever becomes compromised (one of the rat bastards sells it, or it is posted somewhere and harvested), you can always dump it.
There is one major problem with this: all of the legitimate mail you receive at that address goes along with the address, and you will have to track down the websites and services you do want and resubscribe. Heck, if you resubscribe to the same service that compromised your e-mail address in the first place, you won’t have to wait long for spam to start flooding in. And let’s not forget the fact that since you receive legitimate e-mail at that address, even if you don’t get enough spam to consider dumping the address, you still have to sort through it.
This is where email quarantining comes in. Although I just invented that term, the concept is not new. The idea is that you give a different email address each time you sign up with a site. If your mail email address is john@doe.com you might sign up at ebay with john.ebay@doe.com or john-ebay@doe.com. These email “subaddresses” give you the ability to quarantine that account if it ever becomes compromised, without losing all of your other subaddresses, because if you get spam in your inbox, you know exactly where it came from.