Are you going to be sending email in PHP? Don't use the mail() function, unless your site's email needs are very basic and you are running on a Linux/Unix machine. It is light on features and not built in to the Windows version.
The best approach is to use a 3rd party mail program. In the past I have used PHPMailer and I love it. I make many posts with this solution to SMTP email problems in PHP and this is the fix!
Below is the PHP code to use it. Place class.phpmailer.php into your php includes directory.
Replace text in << >> with your server information: http://www.emailaddressmanager.com/tips/mail-settings.html
$mail = new PHPMailer();
$mail->IsSMTP(); // send via SMTP
$mail->Host = "<<smtpserver>>:<<stmpport>>"; // SMTP servers
$mail->SMTPAuth = true; // turn on SMTP authentication
$mail->Username = "<<uname>>"; // SMTP username
$mail->Password = "<<pword>>"; // SMTP password
$mail->From = "<<email address from>>";
$mail->FromName = "<<email name from>>";
$mail->AddAddress("<<email address to>>");
$mail->AddReplyTo("<<email address from>>","<<email name from>>");
$mail->WordWrap = 50; // set word wrap
$mail->IsHTML(true); // send as HTML
$mail->Subject = "Subject";
$mail->Body = "Body text";
$mail->AltBody = $mail->Body;