I just asked this from my VAR. And I got an answer:
SPR 487531 "SMTP notifications still being sent to deleted user when that user was a member of a group if not removed from group before deleting user"
please ask from your VAR about S-036225 to get a SQL script that will fix this. The Solution is not visible for us mortals and I'm not sure can we share the info publicly. Maybe Someone from SolidWorks can comment on the sharing part, Joy Garon?
Thanks Arto. I will get with my VAR and see if they can fix this. Much appreciated!