There are 3 options for this:

1. If customers unsubscribe via the unsubscribe link in your newsletter, they will not receive future newsletters. In this case you do not need to do anything.
2. You can create a list (excel or CSV) with the email addresses of customers who no longer wish to receive newsletters, and import it to Newsletter2Go as a ‘blacklist’.
3. Search for the recipients concerned under ‘Recipients’ -> ‘All recipients’. Check these recipients in the list and then click on ‘Actions for selected recipient’ -> ‘Unsubscribe from address book’.