If a constituent record appears in BBCRM and gets a email via a BBIS mailing that they wish to unsubscribe from you can query the people who unsubscribed from your mailing as long as their was a solicit code associated with the mailing.
Note: If the constituent record does not exist in BBCRM there will be no way to see who unsubcribed from mailings.
1. Create Ad-Hoc Query in BBCRM 2. Include records where you can choose the solicit code you chose in your mailing and where the added by user name is equal to your blackbaudhost\BBNCapppoolxxxx