Unsubscribed Users - caused by black listed sending address.

Working with a client that had an issue, over 12K email addresses got bumped to "unsubscribed" due to her sending email address being placed on a black list.  NOW she wants to get these 12K emails back onto her "subscribed" list.

Easy way to do this?   Tried to delete all the "unsubscribed" and import BUT the system still has the list of previously unsubscribed somewheres.

help!