Ever email sent from NewZapp contains a link for the contact to unsubscribe or manage their preferences and pick which public Groups they wish to belong to.
If you want to unsubscribe a Contact yourself, you can do so from within your account.
NB: This action will permanently prevent the Contact from receiving any of your campaigns. They will be unsubscribed from all Groups in your account.
For more information about the difference between Suppress, Remove and
Unsubscribe please see: