Gmail vs Tomba email finder

The Gmail API gives OAuth-scoped programmatic access to a user's mailbox: reading, searching, sending, and organizing messages, threads, labels, and drafts, with message bodies transported as base64url-encoded MIME inside JSON. It requires a Google OAuth 2.0 bearer token, confirmed live via a `WWW-Authenticate: Bearer realm="https://accounts.google.com/"` challenge on an unauthenticated request, and unlike most server-side email APIs it explicitly supports cross-origin browser calls, echoing the request Origin on both a GET and an OPTIONS preflight.

Tomba's Email Finder API discovers and verifies professional email addresses from a company domain or a person's name, and doubles as a B2B prospecting and lead-enrichment tool via linked domain-search and phone-finder endpoints. It authenticates with a paired `X-Tomba-Key`/`X-Tomba-Secret` header set rather than a single token, and a live Origin-header probe confirms it explicitly supports browser CORS, echoing the request Origin with credentials enabled on both a GET and an OPTIONS preflight.