SMTP Contact Form Blank Screen On Submit

I've been having alot of issues with contact form, does anyone know why my code is just bringing up a blank screen with '(URL)/mail.php when i press Submit on my form. Here is my c

Solution 1:

It's not able to find the php mailer class class.phpmailer.php. Is it in the same directory as as the rest of the files..?

Solution 2:

I would move the header() call outside of the if() statement to make sure a person is ALWAYS redirected: think about what would happen if a person that manually visits yoursite.com/mail.php without using your form to POST data:

<?PHP
ob_start();
if(isset($_POST['btnSubmit']))
{
    // Mail stuff
}
header("Location: $redirect_url");
?>