Proofy - Quickly validate and verify your email lists.
Mail Dump - Powerful Extensions for email addresses extracting, verifying and finding
Breadcrumbs Free Email Verifier - Free forever to validate up to 10,000 emails with 1-click
Castle - The easiest way to protect your users from getting hacked
Email Verification Tool - A Google Sheets add-on for bulk email verification
Truecaller - Find a person by a name or phone number worldwide for free using Truecaller.