To identify other users that may have the same email address selected as their Blackbaud ID username:
1. Core > Users > User list
2. In the Find in list field, enter the email address you're attempting to save as the user's Blackbaud ID username.
3. Review the profiles of any users with that email address to determine who has the email selected as their Blackbaud ID username

An email address can only be used as the Blackbaud ID username for one user. You will need to determine which user should have this email address as their username and remove it from the Blackbaud ID username field for any other users. The email address does not need to be removed from the Email or CC Email fields.