Spam blocker

What is a spam blocker?
A spam blocker is a special type of software, software extension, or even a simple technique that is designed to block unsolicited bulk email or spam. Spam messages are sent in bulk to email users by unsolicited advertisers.

Since many types of spam blockers are simply modified filters, a spam blocker may also be known as a spam filter.
Some spam blockers are real programs, despite being small in size, while some are simply custom configurations in the filtering function of an email client that looks for certain keywords in the subject line of messages.

This type of spam blocker has many limitations. Spam messages that go through the spam blocker are called false-negative, while legitimate emails that are blocked are called false-positive.

Spam blockers and filters have lists of addresses that can either be allowed through or blocked. Addresses that are allowed to pass are put on the “white list”, while those that are to be blocked are put on the “black list”.