Does the job!
NeverBounce - Real-time email verification and cleaning to ensure emails never bounce.
Albacross - The world's first free B2B Lead Generation Network. Albacross help companies master their B2B digital marketing with Lead Generation and targeted marketing
Email Verifier - Email verifier app lets you verify email.
Hunter - Find all the email addresses related to a domain
Email List Verify - The Fastest Way to Improve Email List Deliverability and ROI
Upscribe - Embeddable lead generation forms for Medium