email - Setting SMTP details for php mail () function

I have been looking for an answer and tried many things to this problem.

My script works fine on my webhost but when moving it to an other dedicated server the mail never gets delivered. Now i need to set the SMTP server but don't get it right.

Using Gmail apps btw. This is how the code looks like.

if(!$_POST) exit;

$email = $_POST['email'];


//$error[] = preg_match('/\b[A-Z0-9._%-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b/i', $_POST['email']) ? '' : 'INVALID EMAIL ADDRESS';
if(!eregi("@",$email )){
    $error.="Invalid email address entered";

    $errors=1;
}
if($errors==1) echo $error;
else{
    $values = array ('name','email','telephone','message');
    $required = array('name','email','telephone','message');

    $your_email = "xxx@example.com";
    $email_subject = "New Messag: ".$_POST['subject'];
    $email_content = "New message:\n";


    foreach($values as $key => $value){
      if(in_array($value,$required)){
        if ($key != 'subject' && $key != 'telephone') {
          if( empty($_POST[$value]) ) { echo 'PLEASE FILL IN REQUIRED FIELDS'; exit; }
        }
        $email_content .= $value.': '.$_POST[$value]."\n";
      }
    }


    if(@mail($your_email,$email_subject,$email_content)) {
        echo 'Message sent!'; 
    } else {
        echo 'ERROR!';
    }
}

$mail->Mailer = "smtp";  
$mail->Host = "ssl://smtp.gmail.com";  
$mail->Port = 465;  

$mail->SMTPAuth = true; // turn on SMTP authentication  
$mail->Username = "user@gmail.com"; // SMTP username  
$mail->Password = "password"; // SMTP password 

?>

So how do i set the SMTP settings right?