Can recipients unsubscribe from email lists?

Yes, the unsubscribe link is automatically included in every email. When participants click on the unsubscribe link, they have the option to unsubscribe or update their contact information. 

Respondents that are unsubscribed from an email list will not be sent any

Note: when a participant unsubscribes, they are only unsubscribing from the current list, if they are also on other lists in your account they will still remain subscribed to those lists.