When a customer receives your campaign via email, there will be an option to unsubscribe (or opt-out).

That link will bring them to this screen: https://lab.alpineiq.com/emailSettings/{{storeID}}

Currently, it's just one option to opt-in/out of all communications, as seen in the screenshot below:

Campaigns sent via Text will have the text Reply STOP to opt out appended to each message. Customers can type stop and send a message to that same number and they will be opted-out of text communications.

If they ever made a mistake and want to opt-in again, they will need to resubmit the signup form to trigger a new opt-in request to be sent. See Sharing Signup Forms.

After they submit the signup form again, they will be presented with a message that asks them to "START" to confirm the re-opt-in.