Email Validator   
http://www.bytefoundry.com

Email Validator checks deliverability of email addresses. It does so by first performing a DNS query on the domain name of each email address in order to determine the address of the mail server servicing that domain. Once the mail server is found, a connection is made in the same way as your ISP's mail server would make a connection. Email validator will first attempt to use the SMTP VRFY command to determine deliverability. If the VRFY command is enabled, the mail server will report whether the email address being tested is in fact deliverable, Email Validator will then close the connection and report the result. In many cases the VRFY command is disabled on SMTP servers. If this is the case for any given mail server, Email Validator will then attempt to simulate the delivery of an email message. During this process, the mail server will report whether or not it can accept a message for the email address being tested. Once this is reported, Email Validator will close the connection and report the result. NO EMAIL IS ACTUALLY SENT. Email Validator never gets to that point, so the owner of the email address will not receive any message as a result. Once a list of email addresses has been tested, the user may export all addresses along with test results or simply export all deliverable or non-deliverable addresses in order to clean an existing list or build a new one containing only deliverable addresses. The result for anyone who runs a mailing list, i.e. ezine and newsletter publishers, businesses, political parties, non-profit organizations, etc. can save time and money by sending mail only to deliverable addresses and not have to clean delivery failure notices out of their inboxes.

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.

EmailValidator   
http://www.dimplesoftwares.com

ASP.Net Email Address Validator Control finds invalid email addresses without actually sending an email, in your mailing list or in your website form! ASP.Net Email Address Validator Control is highly scalable email validator solution. Capable of handling large volumes of addresses and it can be easily integrated into your website to check addresses on-the-fly ! Email Validator Control allows you to validate email addresses and MX Records, from any .NET application. Email Validator Control can be used from ASP.NET web pages, to windows forms, to web services. The only limitation to using Email Validator Control is your programming imagination. Email Validation Control first checks syntax of email address before actually checking with SMTP server and mailbox. By default ASP.Net Email Address Validator Control checks your system for your primary DNS server. As a benefit, you can specify specific DNS Servers in the form of a comma-delimited string. ASP.Net Email Address Validator Control will attempt to connect to each one, until a successful connection is made, and then use the first responsive DNS Server for the remainder of the ASP.Net Email Address Validator Control session. Email Validator Control has a built-in high performance internal cache that stores previously looked-up MX Records. For example, once the MX Records for hotmail.com have been determined, Email Validator Control no longer makes the expensive DNS Queries again, to determine those records. Instead, when the 2nd email address is encountered, that belongs to hotmail.com, Email Validator Control checks it's internal cache to see if the records are there, and then uses those records. By default the Email Validator Control cache is set to time out every 15minutes, however, this time can be set by the programmer, to be minutes, hours, or even days! Email Validator Control provides the capability to add addresses to a 'Bad Address' list !