邮件在while循环中不起作用，我该怎么办？

Question

下面的代码不发送任何电子邮件，已经在phpmyadmin中尝试了sql代码，我得到了正确的结果。得到四行，并且每个人在userMail下都有一个有效的邮件。有人能发现我做错了吗？邮件的原始发送已更改为XXX@XXX.XX

我在服务器上的代码中使用邮件，并且邮件可以正常工作，并且邮件功能具有正确的配置。

    $firstPremission = 5;
    $secondPremission = 6;
    $sql = "SELECT * FROM user WHERE permission = ? OR permission = ?";
    $stmt = mysqli_stmt_init($conn);
    if(!mysqli_stmt_prepare($stmt, $sql)){
        header("Location: ../signup.php?error=sqlerror");
        exit();
    }else{
        mysqli_stmt_bind_param($stmt, 'ii', $firstPremission, $secondPremission);
        mysqli_stmt_execute($stmt);
        $userResult = mysqli_stmt_get_result($stmt);
        if(mysqli_num_rows($userResult) > 0){
            while($userRow =      mysqli_fetch_assoc($userResult)){
                $userMail = $userRow['userMail'];
                $msg = "Ny använder är registrerad";

                // use wordwrap() if lines are longer than 70 characters
                $msg = wordwrap($msg,70);

                $headers = 'From: XXX@XXX.XX' . "\r\n" .
                    'Reply-To: XXX@XXX.XX' . "\r\n" .
                    'X-Mailer: PHP/' . phpversion();

                mail($userMail,'New account',$msg,$headers);
            }
        }
    }