MailBee.NET Address Validator
Enables .NET applications to verify bulks of e-mail addresses for correct syntax or existence. Validation levels include RegEx check, DNS MX lookup query, SMTP connection and test send attempt without actual sending a message. Massively multi-threaded for better performance (can process hundreds of thousands of addresses), can take data from string array, DataTable or MS SQL database. Multi-pass, tolerates greylisting. Royalty-free distribution.