Verify outlook.com addresses

How Kavik verifies Outlook.com, Hotmail, Live and MSN addresses: every consumer accept is confirmed through Microsoft Graph Contact Transfer before a valid verdict.

Outlook.com (including hotmail.com, live.com and msn.com) has a treacherous behavior for verifiers: its consumer MX intermittently accepts nonexistent recipients. A verifier that trusts a 250 at RCPT will mark dead addresses valid.

How Kavik verifies Outlook

  • Every consumer accept is confirmed through Microsoft’s GetCredentialType (GCT) API before it becomes a valid verdict. If the SMTP conversation says yes but GCT says no, the address is not called valid.
  • Stray accepts are logged and measured rather than trusted, which keeps Microsoft consumer false valids off your list.
  • Microsoft 365 business tenants get their own handling; tenant catch-all behavior is measured rather than assumed.

What the verdicts mean here

  • Valid: accepted at SMTP and confirmed through GCT.
  • Risky: the domain answered ambiguously or the tenant is catch-all.
  • Invalid: Microsoft definitively said no such user.
  • Unknown: throttled or greylisted this time; never billed.
curl "https://api.kavik.email/api/v1/verify?email=jane@outlook.com" \
  -H "X-API-Key: eva_your_key"

See single verification for the full response shape.