Remove Subscribers from Blacklist

There are two ways to do that:

1. The subscriber re-subscribes using the subscription page. When they confirm the subscription by clicking the confirmation link they are removed from the blacklist automatically.
2. You can sometimes manually remove a subscriber from the blacklist. To do so :

search for the subscriber -> view their profile -> click history -> click subscription

You will see a button to manually remove them from the blacklist.
If the button is not there, this means the subscriber marked one of your emails as spam and you need to ask them to sign up again.