In some rare cases, you could receive an error when editing a client user's email address. What causes the error? If the user's email address has been set up as a client user in Snapdocs previously, and you use that email address to update an existing client user you will receive an error that states "That email is already in use by another one of your clients."
If you are creating a new client user account with the email address, you will receive no error. The only way to resolve this is to deactivate the current client user account that you are trying to update and create a new one.