NeverBounce - Real-time email verification and cleaning to ensure emails never bounce.
Elucify - A completely free software tool that uses crowdsourced data to find business email addresses
Email List Verify - The Fastest Way to Improve Email List Deliverability and ROI
Lead Forensics - B2B website analytics and lead generation.
ZeroBounce - Removes invalid emails from your list to prevent email bounces from ruining your deliverability.
FindThatLead Prospector - Feed your sales team with daily leads.