Unsubscribe link

Pretty basic question that has me stumped: Is an automatic “unsubscribe” link added to email newsletters sent via eTap or do we need to add a link when we create the newsletter? For example, one of the templates I'm working with has a text block at the bottom that reads: About Us | Contact | Unsubscribe. I can obviously add the links for the first two but the third one, I have no idea where to link. Thanks!