An automated process in which a robot program searches Web pages or other Internet destinations for email addresses. The program collects the address into a database, which frequently gets resold to spammers or unethical bulk mailers. Many U.S. state laws forbid harvesting. CAN-SPAM does not outlaw it by name but allows triple damages against violators who compiled their mailing lists with harvested names.

The 3 Things To Avoid When Emailing Your List
When you decide to have an opt-in list, it is not just a matter of sending your subscribers your promotional newsletters or catalogs.

