Antideo - Email, IP address and phone number validation API service
Proofy - Quickly validate and verify your email lists.
Numverify - Global phone number validation and lookup API
Trumail - Free email verification API
RealValidito - Phone Validator | Free Phone Number Validation & Phone Number Lookup Service | Realvalidito
Email List Verify - The Fastest Way to Improve Email List Deliverability and ROI