NeverBounce - Real-time email verification and cleaning to ensure emails never bounce.
BizProspex - BizProspex offers CRM data cleaning solutions.
Email List Verify - The Fastest Way to Improve Email List Deliverability and ROI
RingLead - RingLead offers a complete end-to-end suite of products to clean, protect, and enhance company and contact information.
NoBounce Email List Cleaner - Email list validation & cleaning maximizes the efficiency of your email marketing campaigns and protects your email sender reputation.
TowerData - demographic data on email addresses