What is double opt-in?

Permission marketing process implemented by some companies for security reasons to complement conventional opt-in forms. After requesting the inclusion of their email address in a mailing list, the potential subscriber receives a verification message in their inbox specifying the requirement of a last action to confirm their voluntary entry. In the same way, from now on you will be asked to confirm your registration before reading the emails that you receive. This mechanism makes it impossible to register any recipient on a list without their consent.