CSMail Developer Edition   
http://www.codestone.ltd.uk

The Internet Mail Client Control Library is a suite of ActiveX/COM objects providing SMTP (RFC 821), POP3 (RFC 1725) and MIME (RFC 1341) support for application developers. The library is suitable for use in Visual Basic, C++, Delphi and scripting languages such as ASP, VBScript/JScript and VBA. Support for SOCKS 4 and 5 proxies is built into the SMTP and POP3 objects together with support for standard SMTP and POP3 proxies. ESMTP authentication is supported in the SMTP object. The Message Object Model provides a simplified, but flexible, implementation of the MIME standard including support for multipart MIME messages and the standard encoding mechanisms. A COM interop assembly is included for .NET developers.

Smtp.NET   
http://www.exclamationsoft.com

Professional Email Component for ASP.NET and .NET Windows Forms which doesn’t extend the System.Web.Mail namespace but was built from the ground up to go further and offer you more. Smtp.NET was designed to be the easiest .NET email component to learn and use, unlike competitors that require you to learn their object model simply to send an email. Features HTML Email with automatic image embedding, authentication, automatic ZIP compression of attachments, support for message queuing on IIS & emailQ.NET, mail merge, multiple attachments, multiple recipients, specify multiple servers for failover and redundancy, and more. Smtp.NET is installed in the GAC (Global Assembly Cache) for easy access by all of your developers. Smtp.NET is feature rich and offers functionality that the System.Web.Mail.SmtpMail class cannot. Fully supported and documented with extensive examples to jump-start your application development. Royalty-free redistribution licenses, site-wide licenses, and multiple user discounts are available.

Pivo Email Validator Component   
http://www.pivo.com

Having problems with the email addresses in your mailing list?Are you tired of getting bounce backs every time you perform a mailing? Email Validator will solve your email validation problems. Email Validator is an assembly that requires the Microsoft .NET framework to run. It is used to validate email addresses at different levels. Email Validator does not have a GUI front end, it is a server component that can only be accessed programmatically. Email Validator can be used on signup forms or it can validate huge lists of email addresses from one address to million. Email Validator validates email addresses at four different levels. Syntax, Domain, SMTP, and Mailbox levels. To validate an email address, simply create the EmailValidator object, pass it the email address and the level of validation to check, and Email Validator will do the rest. For some code examples on how to use Email Validator, click here. Email Validator does not actually send an email, but it can check the remote mail server to see if the server will accept an email for that address. The only way to truly check to see if an email address is valid, is to send an email. Here's a more detailed explanation of the 4 levels of validation provided by Email Validator.