Anti-spam techniques
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.

Anti-spam techniques can be broken into four broad categories: those that require actions by individuals, those that can be automated by e-mail administrators, those that can be automated by e-mail senders and those employed by researchers and law enforcement officials.