Opt-Out: An opt-out is an action taken by a subscriber who wishes to be removed from an email list or similar notifications. It is generally associated with direct marketing by mail, telephone or email. Those who unsubscribe are placed on what is called a Robinson List. A non-Internet example in the United States is the National Do Not Call Registry.
The Federal CAN-SPAM Act (Controlling the Assault of Non-Solicited Pornography and Marketing Act), passed by Congress in 2003, requires that commercial emails have visible and operable unsubscribe functions in the form of a clickable link or button. It is therefore illegal to ignore requests to be removed from an email list, and if the opt-out is not honored within 10 days, the sender becomes subject to fines.
Spammers sometimes further exploit this required capability by sending emails with fraudulent opt-out buttons. Instead of unsubscribing the user as it purports to, the button will instead verify that the email address is active, thereby providing the spammers with a list of legitimate email addresses and subjecting users to even more spam.
A marketing campaign that automatically signs website users up for emails or obtains email lists in other ways is called an opt-out campaign. This allows for a list to be built quickly, but can annoy users who don't remember the fine print saying they'd be receiving emails. Many legitimate websites instead use opt-in campaigns, which ask users to sign up specifically for emails or check an additional box when registering on the site. This lessens the likelihood of users flagging emails from a certain company as spam. Damage to a sender’s reputation can result in the email platform tagging all email that company sends as spam, filtering it before it even gets to many users’ inboxes.