如何添加电子邮件服务器& &;端口到这个PHP

我有一个PHP代码在我的服务器中，如果数据被添加到数据库中，它发送邮件给管理员。最近我买了一个虚拟主机并上传了我的文件。问题是我的邮件从服务器得到延迟，所以我问网站托管。他们让我添加这个"rel-hosting.secureserver.net"，并在PHP中添加端口25，以便快速接收邮件。我不太懂PHP。你能帮我把它插入到下面代码的什么地方吗?

<?php
// get data 
$name = $_POST['name'];
$alamat = $_POST['alamat'];
$kota = $_POST['kota'];
$provinsi = $_POST['provinsi'];
$name2 = $_POST['name2'];
$date_n_time = $_POST['date_n_time'];
$phone = $_POST['phone'];
$order_list = $_POST['order_list'];
$comment = $_POST['comment'];
$emails = $_POST['email'];
$sql_query = "set names 'utf8'";
$stmt = $connect->stmt_init();
if($stmt->prepare($sql_query)) {    
    // Execute query
    $stmt->execute();
    // store result 
    $stmt->close();
}
// insert data into reservation table
$sql_query = "INSERT INTO tbl_reservation(Name, Alamat, Kota, Provinsi, Number_of_people, Date_n_Time, Phone_number, Order_list, Comment, Email) 
                VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";
$stmt = $connect->stmt_init();
if($stmt->prepare($sql_query)) {    
    // Bind your variables to replace the ?s
    $stmt->bind_param('ssssssssss', 
                $name,
                $alamat,    
                $kota,  
                $provinsi,  
                $name2, 
                $date_n_time, 
                $phone, 
                $order_list,
                $comment,
                $emails
                );
    // Execute query
    $stmt->execute();
    $result = $stmt->affected_rows;
    // store result 
    //$result = $stmt->store_result();
    $stmt->close();
}
// get admin email from user table
$sql_query = "SELECT Email 
        FROM tbl_user";
$stmt = $connect->stmt_init();
if($stmt->prepare($sql_query)) {    
    // Execute query
    $stmt->execute();
    // store result 
    $stmt->store_result();
    $stmt->bind_result($email);
    $stmt->fetch();
    $stmt->close();
}
// if new reservation has been successfully added to reservation table 
// send notification to admin via email
if($result){
    $to = $emails;
    $subject = $reservation_subject_2;
            $message .= "Dear " .$provinsi."'r'n";
    $message .= $reservation_message_2."'r'n'n";
            $message .= "Pick Drop :" .$name2."'r'n";
    $from = $admin_email;
    $headers = "From:" . $from."'r'n".
    mail($to,$subject,$message,$headers);
    echo "OK";
}else{
    echo "Failed";
}?>