Trumail - Free email verification API
Proofy - Quickly validate and verify your email lists.
Email List Verify - The Fastest Way to Improve Email List Deliverability and ROI
NeverBounce - Real-time email verification and cleaning to ensure emails never bounce.
Verifier - Weed out disposable, non-existent domains or invalid emails.
ZeroBounce - Removes invalid emails from your list to prevent email bounces from ruining your deliverability.