1. Maybe in the settings disable the use of mail(). It's a hell hole and its usually switched off, because need to send mail via smtp. so check the settings.
2. mail() in win does not behave as on unix. What is your OS?
3. Get everything you can for the test, special characters, word wrap, the second recipient enail etc. Check on the basis. Simple headings, text, 1 email. The recipient does not mail.ru and analogues, as their spam filter just eat sent via mail() letter.
4. Why did You decide that's not working? The fact that it does not reach, not a sign that it is not sent.