What Is Confirmed Opt-In?
Confirmed Opt-in or sometimes referred to as double opt-in requires a subscriber to answer an email verification as a way to be put on the opt-in list. If perhaps the contact does not respond, this individual will not get extra emails from you and will be displayed as unconfirmed. This could certainly lower bounced email addresses because of spelling flaws.
Some countries email marketing laws require a confirmed opt-in procedure to help protect SPAM.
Below is an example of a confirmation email.