Anti Spam is a technique used to prevent any unsolicited electronic junk mail or junk newsgroup postings. This in turn saves time, money, network bandwidth and prevents mail server clogging.
Current anti-spam solutions fall into four primary categories: filters, reverse lookups, challenges, and cryptography. Each of these solutions offers some relief to the spam problem, but they also have significant limitations.
Spam wastes time, clogs mail servers and contains fraudulent and offensive content Most mailboxes today are constantly flooded with SPAM - unwanted advertising of any kind. Today more than 50% of all mails worldwide are spam mails.
While there are no shortage of solutions to this ever-growing problem, there are a number of anti spam solutions and anti spam programs available.
The word "Spam" as applied to Email means Unsolicited Bulk Email ("UBE").
Unsolicited means that the recipient has not granted verifiable permission for the message to be sent. Bulk means that the message is sent as part of a larger collection of messages, all having substantively identical content. A message is Spam only if it is both Unsolicited and Bulk.
- Unsolicited Email is normal email (examples: first contact enquiries, job enquiries, sales enquiries)
- Bulk Email is normal email (examples: subscriber newsletters, customer communications, discussion lists)
Source: Spamhaus Project | 
