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Unfortunately, because the email address of the user is directly connected to the Identity Provider used to control access to Twingate, users are unable to update their email addresses for existing accounts within Twingate, and Twingate support has no ability to modify it on the back end.
The easiest solution to needing to change a users email is to simply add the new email as a user within Twingate, and have the new user start to log in with that account rather than their original account.