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 !

CONTACTUS   
http://www.toucanmultimedia.com

Contactus is a professional, spammer-proof contact form for your website. It has a professional appearance that is fully customizable. It is simple to install, requiring only the addition of the receiving address(s) for configuration. And best of all, spammers cannot discover your email address! Free version has advertising links, commercial version does not.

CONTACTUS   
http://www.toucanmultimedia.com

Contactus is a professional, spammer-proof contact form for your website. It has a professional appearance that is fully customizable. It is simple to install, requiring only the addition of the receiving address(s) for configuration. And best of all, spammers cannot discover your email address! Free version has advertising links, commercial version does not.

Rock Solid Contact US System   
http://www.rebusnet.biz

A secure Contact US web form write in PHP, with optional visual confirmation, optional email confirmation, internationalization, easy to customize with template. Keep email private, eliminate 99.99% undesired spam. Prevent bot automation and invalid/spoof email. Double validations client/server keep resources used to minimum. Features: Template System. ( web page & email ) Optional Visual Confirmation. Optional Email Confirmation. English and French supported at this time. Basic support for Bi-Directional text. Time for email confirmation configurable. Private secret string used for request integrity. Page counter and advanced counter. Optional database auto prune. Time validity for visual confirmation configurable. Visual Confirmation (image) full configurable. background color, font color, font size, font rotation, number of digits, random mask , and more ...

Email-Validation   
http://ezinedesigner.com

Example of how Javascrpt and PHP can work together to provide simple and extensible email form validation. Use this as a starting point for more complex server-side validation without screen refresh.