ZeroBounce - Removes invalid emails from your list to prevent email bounces from ruining your deliverability.
Verimail - Clean up email-address lists of any size or use our powerful API for real-time verification.
NeverBounce - Real-time email verification and cleaning to ensure emails never bounce.
DeBounce - Email Validation, Email Checker, Data Enrichment and Appending Tool. Using DeBounce remove invalid, disposable, spam-trap, syntax and deactivated emails.
Email Verifier - Email verifier app lets you verify email.
TheChecker.co - Accurate email verification at low prices.