Hi,
Thank you for reaching out. I see that you'd like to get the user email from a Client ID. You can try to log into your Google Ads account and then open the
Google API console, and check each project and OAuth info if the ClientId and ClientSecret matches the ones you're using. If they match, that means these OAuth credentials are from the email that the user used to log in to their Google Ads account.
Otherwise, this isn't possible via AdWords API. Our top priority right now is to get the new Google Ads API ready for general availability. As such, we aren't planning on adding enhancements to the AdWords API, but we will continue to fully support it, and address any bugs as they are found. For more information on the state of the Google Ads API, please read the blog post at
https://ads-developers.googleblog.com/2020/05/update-on-google-ads-api-beta.html. Let me know if you have further questions.
Thank you,
Bryan, Google Ads API Team

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