In backstage we have the availability to pass the user profile details including email something like this in the issued accessToken:- 

 
profileInfo =

{               email: email,               displayName: name,               picture: picture,             }

;
            
ctx.issueToken({
                claims:

{                   sub: userRef, // The user's own identity                   ent: ownershipRefsArr, // A list of identities that the user claims ownership through                   email: emailId,                   profile: profileInfo,                 }

,
              });