From Elcom Soft:
Mailing lists and address books verifying to determine which of email addresses are dead. The program is multithreaded, so high speed of verifying is provided. Supports ODBC SQL (to extract emails from external sources); works with Socks5 proxy (to use in LAN). COM interface allows integrating it into your own software and web pages; samples for MS IIS and ColdFusion are provided.