Spam is unsolicited and unwanted email. Other common names of spam are spam mail, bulk email or just junk mail. Anti spam appliance basically stop these nasty emails from reaching your inbox. It is a piece of software that identifies and isolates such email. To prevent e-mail spam, both end users and administrators of e-mail systems use various anti-spam techniques. Some of these techniques have been embedded in products, services and software to ease the burden on users and administrators. No one technique is a complete solution to the spam problem, and each has trade-offs between incorrectly rejecting legitimate e-mail vs. not rejecting all spam, and the associated costs in time and effort.