Double opt-in

"Double opt-in" means a new subscriber must click a link in a confirmation email before they join your list. It proves the email is real and that the person really wanted to sign up.

Switch it on in Marketing → CRM → Subscribers → Ask new subscribers to confirm their email.

When it is on:

• someone who signs up from your store gets an email titled Please confirm your subscription;
• they show as Waiting to confirm in your list and get no newsletters yet;
• after they click Confirm subscription they become Active;
• if they never click, nothing is sent to them. They can sign up again for a new email.

People you add yourself or import from a CSV are not asked to confirm: by adding them you are saying they already agreed.

Someone who unsubscribed stays unsubscribed. Confirming an old link does not bring them back.