Lydia Kopf

I had the same issue and found a different workaround. It's annoying, but it worked.  

Step 1. Change the requester on the ticket temporarily; 2. Delete the user with the email issue; 3. Create a new user for that individual; 4. Switch the requester on that ticket back to the new user that you recreated.

Note: I have not tried this with users who have old tickets that are closed. 

Also, make sure to write down details you will need to re-add when you recreate the user, e.g. org, phone number, etc.