How to read gmails of all users in same domain using imperso

I'm trying to develop one c# console app to read emails using service account without user's consent but I am not getting proper guidance how to achieve it? I have followed steps as per domain wide delegation of authority but it redirects to authorization screen to ask permission.

Actually I want to develop solution like Exchange api streaming notification where I can read email when new event occurred on server and insert it into database using impersonated user.

Please help and thank you in advance.