The Enhanced WP Contact Form plugin for Wordpress is one of a few handy contact forms that are easily to added to your wordpress site. However, if you try to use it on a wordpress site hosted on a windows server you may get an error massage similar to the following when you hit the 'submit' button on the contact form:

Warning: mail() [function.mail]: SMTP server response: 501 5.5.4 Invalid Address in \wp-content\plugins\enhanced-wordpress-contactform\wp-contactform.php on line 178