A spam trap comes in 2 varieties:

•  An old email address that has been reactivated and used to collect mail sent to it.
  
• An address created and placed on various websites, but has and will never sign up for anything.

ISPs take old email addresses and repurpose them into spamtraps. During the time (and this time varies at each ISP; however, it is usually fairly substantial) the address was abandoned or account was discontinued, the ISP will bounce incoming mail with a “User Unknown” (or equivalent) message. A reputable mailer will realize that the account is no longer active and remove the address from their list or database.

Another form of spamtrap (sometimes referred to as a “honeypot”) is an address (and sometimes domains) that is created and placed on various pages on the Internet. These addresses are never used for anything other than accepting mail that comes into them and analyzing it for blocking/reputation purposes. The only way these addresses can appear on a list are:

• The list was formed from “scraped” addresses. This means that the sender did not attain proper permission from the “subscriber”.
  
• The list was rented or purchased (also points to improper permission).

Sending mail to a spamtrap can mean the difference between message acceptance and blocking as well as Inbox and Bulk folder placement. As many anti-spam systems are starting to rely more on “reputation”, it is important to adhere to proper permission and use a service that properly manages bounces. This will assist in establishing and maintaining a good reputation, message delivery and placement.