Old post, but might be helpful for someone..

"UniqueClaimTypeIdentifier" refers to a property within the AntiForgeryToken mechanism that specifies the specific claim type used to uniquely identify a user within a claims-based identity system, essentially defining which claim within a user's identity should be used to verify their authenticity for security purposes like anti-forgery token validation. It is a string value that indicates which claim type should be considered as the primary identifier for a use.

You are using Email for this.