PHP mail(） - 作为垃圾邮件传递(使用 PHP 邮件库）

require("class.phpmailer.php");
$mail = new PHPMailer()
$mail->From = "sender@gmail.com";
$mail->AddAddress("recipient@gmail.com");                 // name is optional
$mail->AddReplyTo("sender@gmail.com");
$mail->WordWrap = 50;                                    // set word wrap to 50 characters
$mail->IsHTML(true);                                  // set email format to HTML
$mail->Subject = "Here is the subject";
$mail->Body    = "This is the HTML message body <b>in bold!</b>";
$mail->AltBody = "This is the body in plain text for non-HTML mail clients";
if(!$mail->Send())
{
   echo "Message could not be sent. <p>";
   echo "Mailer Error: " . $mail->ErrorInfo;
   exit;
}
echo "Message has been sent";

我不知道我需要添加哪些标题，以不作为垃圾邮件发送电子邮件，我如何使用它？

//$mail->IsSMTP(); // is this necessary?
//$mail->Host = "some host ip";  // what i need to write here?
//$mail->SMTPAuth = true;     // is this necessary to send email NOT as spam?
//$mail->Username = "test";  // and this?
//$mail->Password = "secret"; // and this?

谷歌搜索了一段时间，我没有找到任何关于如何发送电子邮件而不是垃圾邮件的明确信息......有什么想法吗？