How Spammers Verify Email Addresses

Spammers can verify email addresses in three ways: by receiving replies, providing an opt-out web link, and by using web bugs. Web bugs are small images that secretly track information about the spam recipient. The following section describes a web bug in detail. A recipient of spam may occasionally reply to a spammer's email. This is a futile gesture. Often, the spam email is sent from a fictional email address, and the reply will be returned, undelivered. Spam can also be sent from a real, but hijacked address. Hijacking occurs when the spammer chooses a bona-fide email address to use in the mail headers of his or her spam, either the From: header or the Reply-To: header. The unfortunate victim will receive thousands of bounced messages from undelivered emails, as well as the occasional irate reply.

Note

One golden rule about spam is never to reply and never to click an opt-out link.

Email is occasionally sent from an account set up by the spammer. If...