From what I can find, every way described in related questions is now obsolete or requires a user to authenticate/authorize sharing the profile information.
Examples: Retrieving a user's public google/gmail picture | Google Users photos API - get the public user photo without authenticating
However, when I add custom/business inboxes to my Gmail app on Android (from my own hosting/domains, using IMAP, 100% unrelated to Google),
any clients (who are NOT in my Google/Android contacts) that send emails to my business accounts, using their Gmail address, the Gmail app will display their public profile picture.
So, there must be a way I can get anyone's public profile picture by simply providing their email address, even if I have to authenticate through my own account (rather than asking other users to authorize sharing their info).
Does anyone know how this can be done?
Basically, I don't want to have to use the Gmail app to be able to get the picture. I want to do this from outside the Gmail app, programmatically.
(any language, any platform)