Google

Provides the email capability via Gmail's REST API: list, search, read, send, and reply.

Requirements

RequirementNotes
Gmail API + OAuth consent screenRequests gmail.readonly, gmail.send, userinfo.email. The first two are restricted scopes — until the app is verified, only accounts added as test users can grant them.
OAuth 2.0 client, type iOSOne per Bundle ID (dev and production need separate clients). Redirect URI isn't configurable — Google fixes it to the reversed client ID, which Eigin computes automatically. Only set up for iOS today; expanding Eigin to another platform will need its own OAuth client, since Google's client types are platform-specific.
EIGIN_GOOGLE_OAUTH_CLIENT_ID_STAGING / _PRODUCTIONSet in .env (see .env.example), wired into the app via EiginGoogleOAuthClientID in Info.plist. Connecting Google fails fast with a clear error if this is missing.
Setup processManual only, through the Google Cloud console — Google has no API for creating this kind of OAuth client, so it can't be codified.

Google's consent screen lets scopes be approved individually. Denying one still connects the account, but Eigin only exposes tools for what was actually granted — the connection detail screen shows which.