In Blackbaud Sphere, users can setup eNewsletters to be sent out to their constituents alerting them to upcoming events and campaigns. This solution outlines how to remove a Contact from an eNewsletter Subscriber Base without deleting the email address from the Contact record.
Log into Sphere and go to Communications > eNewsletter
Hover over the eNewsletter and choose Subscriber Base
Mark the box next to the record you want removed and click Delete