How to change email address of existing user in SAP Sourcing?

As a security analyst, I need a workaround for the issue in SAP Sourcing wherein the email address of the user must be changed.

Upon trying changing in user admin, it does change there but the email address in Sourcing itself cannot be changed.

I tried deleting but there is no delete function. I tried setting a dummy account to inactive but it doesn't delete and I can't find or recreate the user anymore.

Is there a possible way to do this or the user has to accept that it won't be changed anymore?