A spamblock is a text segment interjected into an e-mail address to foil a spambot (a program that a spammer uses to troll the Internet seeking e-mail addresses). The idea is that a human will understand the message, and remove the spamblock from the address, while a spambot will simply collect addresses automatically, usually by collecting any uninterrupted text string that includes the @ symbol. In general, it isn't time- or cost-efficient for a spammer to sort through addresses manually to remove spamblock. Most messages sent to an address with a spamblock will be returned to the sender as undeliverable bounce e-mail.
Although any added text -- even a single character -- can render an e-mail address invalid, most often a spamblock is a self-explanatory phrase, such as "NOSPAM" or "Delete_this_sentence." A spamblock should be positioned to the right of the @ symbol, and before the valid domain name, so that the spam is not accepted by your service provider's server, forcing them to deal with the undeliverable mail. The resulting e-mail address might look something like this:
editor@Delete_this_sentence.whatis.com.
To ensure that legitimate correspondents understand what to do, people sometimes add a message instructing the reader to remove the spamblock from their address before sending e-mail. Using a spamblock is sometimes known as munging an address.