Can I reactivate unsubscribed subscribers?

Unsubscribed subscribers are all subscribers who have unsubscribed from your newsletter. They have used the unsubscribe link in your newsletter to let you know they no longer want to receive your newsletter. Unsubscribed subscribers also includes subscribers you have removed from your active subscriber list yourself. Lastly, this category includes the subscribers who have unsubscribed using the Gmail or Outlook.com web interface. 

You can add an unsubscribed subscriber back into your list of active subscribers. To do so, click the box for the subscriber. You will then get the option to either activate your subscriber(s) or to delete them permanently. Please note: you can only re-activate your subscriber if they have given you explicit permission to send them a newsletter.