Contact Support and reference this article.  and provide a written notice by the user (from the affected email address) that they would like to be removed from the opt out list.
We need evidence that this was sent from the affected email address.  The written notice must also explicitly state the person's intent to continue receiving emails from your organization. 

As a suggestion, to get the correct documentation evidence, create a forward of the original email. From that forwarded text cut and paste the full details.  As an example:

From: Deb XXXX  []
Sent: June 07, 2012 4:32 PM
To: Todd Fuqua
Subject: RE: Help!

I want to continue receiving emails from Blackbaud.  Please take me off your opt-out list.  My email is