I use the latest WAMP and I get this when I try to send emails:
Warning: mail() [function.mail]: Failed to connect to mailserver at \"localhost\" port 25, ve
You are not running an smtp server on your machine, but you don't have to. Just set SMTP to a open smtp server for example:
ini_set('SMTP', 'smtp.yourisp.com');
Take a look at your ISP's home page or http://www.e-eeasy.com/SMTPServerList.aspx for list of SMTP servers.
If you have a desktop mail program, you can use the same address as you use for outgoing mail.