Mailcheck - An application to clean your subscription list from bounces, and enrich data with the customers
Proofy - Quickly validate and verify your email lists.
mailfloss - Bulk email verification for busy businesses and email marketers. Put your email validation on autopilot. One-time, 60-second setup, no developers needed. Get your emails delivered to real people and maximize your email ROI.
Trumail - Free email verification API
Reacher - Check if an email exists without sending any email.
Email List Verify - The Fastest Way to Improve Email List Deliverability and ROI