(In non-service-account scenarios, your application calls Google APIs on behalf of end-users, and user consent is sometimes required.) Note: These service-account scenarios require applications to create and cryptographically sign JSON Web Tokens (JWTs). We strongly encourage you to use a library to perform these tasks.
All of my google email accounts (3 total) transferred with no issues. My Outlook work email and my personal Hotmail accounts didn't transfer. When I try to sign into my Outlook work email, it first takes me to the login username page that looks like I'm signing into a Gmail account then tells me that my password is incorrect.