Since you didn't include the class your using. Your code above doesn't have the New Object even set.
In your case it would be some thing like this
$mail = new Sendmail("host","user","pw");
$mail->SMTPAuth = true;
How ever. You should just use the PHP Send Mail. All so check your spam folder too. and your SMTP logs and make sure your not getting any errors when the message is getting sent.
Try posting the class object your using.