Two things-- Turn on full error reporting:
PHP Code:
error_reporting(E_ALL);
ini_set("display_errors", 1);
And check the success of the mail() function-- you assign the result to variable $success but then you don't check it.
PHP Code:
if (!$success) {
die("error sending email!");
}
If the mail() function fails check your PHP error log.
If all of that doesn't get you anywhere, tell us what kind of PHP install you are using and dump the contents of your phpinfo() here.