If you no longer have access to the Google account or Gmail address and want to use a different email, refer to I need to change my email from a Gmail account to a non-Google email address.
Here is a sample email:
---------- Forwarded message ----------
From: Blackbaud Authentication Services <DoNotReply@blackbaudondemand.com>
Date: Fri, Apr 21, 2017 at 5:18 PM
Subject: Reset your Blackbaud account password