Opt-out

Instead of giving people the option to be put in the list, they are automatically put in and then have the option to request to be taken out.

Opt-in email [1] is a term used when someone is given the option to receive "bulk" email, that is, email that is sent to many people at the same time. Typically, this is some sort of mailing list, newsletter, or advertising. Without obtaining permission before sending email, the email is unsolicited bulk email, better known as spam.

Unconfirmed opt-in
Confirmed opt-in (COI)