Proofy - Quickly validate and verify your email lists.
Mail Dump - Powerful Extensions for email addresses extracting, verifying and finding
BriteVerify - Email Validation & Email Verification reduces bounce rates up to 98%. Rapidly verifying email addresses has never been easier, just drag drop and deliver!
Castle - The easiest way to protect your users from getting hacked
Trumail - Free email verification API
Truecaller - Find a person by a name or phone number worldwide for free using Truecaller.