NeverBounce - Real-time email verification and cleaning to ensure emails never bounce.
ZeroBounce - Removes invalid emails from your list to prevent email bounces from ruining your deliverability.
Email List Verify - The Fastest Way to Improve Email List Deliverability and ROI
BriteVerify - Email Validation & Email Verification reduces bounce rates up to 98%. Rapidly verifying email addresses has never been easier, just drag drop and deliver!
Email Verification on Google Sheets - An add-on for email verification directly in Google Sheets
TheChecker.co - Accurate email verification at low prices.