PHPMail 电子邮件未发送 - 显示邮件发送失败

Question

**下面是我的邮件功能没有错误显示但邮件未发送**

$message=$_POST['message'];  
         $to='kesavan197@gmail.com';
        $sub="Product Booking";
         $msg="Product Title : ".$ptitle."     , Type: ".$typ."   , KG: ".$kg."    , Name: ".$name."  , Mobile: ".$phone_number."   , Email: ".$email."   , Flavour: ".$flavour."   , Message: ".$message."    , Amt: ".$amt;
         
        $header = "From: $email\r\n";
        $header.= "MIME-Version: 1.0\r\n";
        $header.= "Content-Type: text/html; charset=ISO-8859-1\r\n";
        $header.= "X-Priority: 1\r\n";
        $header .= "X-Mailer: PHP". phpversion() ."\r\n";
        $status = mail('$to', $sub, $msg, $header);
         
        if($status){
          echo "Thank you for using our mail form";
        }else{
          echo "Mail sending failed."; 
            }

输出是
邮件发送失败。