PHPMailer SMTP Self Hosted Server

<?php
error_reporting(0);

// Download PHP mailer from github
// https://github.com/PHPMailer/PHPMailer/archive/master.zip

// Install PHP mailer composer using this command
// composer require phpmailer/phpmailer

/**
 * This example shows settings to use when sending via Google's Gmail servers.
 * This uses traditional id & password authentication - look at the gmail_xoauth.phps
 * example to see how to use XOAUTH2.
 * The IMAP section shows how to save this message to the 'Sent Mail' folder using IMAP commands.
 */
//Import PHPMailer classes into the global namespace

// These must be at the top of your script, not inside a function
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;
use PHPMailer\PHPMailer\SMTP;

//Load composer's autoloader
require './vendor/autoload.php';
//Create a new PHPMailer instance


$mail = new PHPMailer;
//Tell PHPMailer to use SMTP


$mail->isSMTP();
//Enable SMTP debugging
// SMTP::DEBUG_OFF = off (for production use)
// SMTP::DEBUG_CLIENT = client messages
// SMTP::DEBUG_SERVER = client and server messages

// $mail->SMTPDebug = SMTP::DEBUG_SERVER;

//Set the hostname of the mail server
$mail->Host = 'domain.com';

// use
// $mail->Host = gethostbyname('smtp.gmail.com');
// if your network does not support SMTP over IPv6
//Set the SMTP port number - 587 for authenticated TLS, a.k.a. RFC4409 SMTP submission
// $mail->Port = 587;
$mail->Port = 465;

//Set the encryption mechanism to use - STARTTLS or SMTPS
// $mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;
$mail->SMTPSecure = 'ssl';

//Whether to use SMTP authentication
$mail->SMTPAuth = 'true';
//Username to use for SMTP authentication - use full email address for gmail
$mail->Username = "zahid@domain.com";
//Password to use for SMTP authentication
$mail->Password = "111111111111";

//Set who the message is to be sent from
$mail->setFrom('info@semgenius.com', 'Michael Grim');
//Set an alternative reply-to address
// $mail->addReplyTo('replyto@example.com', 'First Last');
//Set who the message is to be sent to

$mail->addAddress('zahid@domain.com', 'Michael Grim');
//Set the subject line

$message ='';
$first_name = $_POST['first_name'];
$last_name = $_POST['last_name'];
$phone = $_POST['phone'];
$email_address = $_POST['email_address'];
$question_comment = (!empty($_POST['question_comment'])) ? $_POST['question_comment'] : 'Message';


$mail->Subject = 'New Message has been received!';
//Read an HTML message body from an external file, convert referenced images to embedded,
//convert HTML into a basic plain-text alternative body
// $mail->msgHTML(file_get_contents('contents.html'), __DIR__);

// Message HERE with Post Form Values
$message .= "<h4>A New Message has been received from: ".$first_name." ".$last_name." </h4>";

$message .= '<p>First Name: '.$first_name."</p>";
$message .= '<p>Last Name: '.$last_name."</p>";
$message .= '<p>Phone Number: '.$phone."</p>";
$message .= '<p>Email Address: '.$email_address."</p>";
$message .= '<p>Message: '.$question_comment."</p>";

$mail->msgHTML($message);


//Replace the plain text body with one created manually
$mail->AltBody = 'This is a plain-text message body';
//Attach an image file
// $mail->addAttachment('images/phpmailer_mini.png');
//send the message, check for errors
if (!$mail->send()) {
    echo "Mailer Error: " . $mail->ErrorInfo;

} else {
    echo "Message sent!";
    header("Location: thank-you.html");
    die();
    //Section 2: IMAP
    //Uncomment these to save your message in the 'Sent Mail' folder.
    #if (save_mail($mail)) {
    #    echo "Message saved!";
    #}
}
//Section 2: IMAP
//IMAP commands requires the PHP IMAP Extension, found at: https://php.net/manual/en/imap.setup.php
//Function to call which uses the PHP imap_*() functions to save messages: https://php.net/manual/en/book.imap.php
//You can use imap_getmailboxes($imapStream, '/imap/ssl', '*' ) to get a list of available folders or labels, this can
//be useful if you are trying to get this working on a non-Gmail IMAP server.
// function save_mail($mail)
// {
//     //You can change 'Sent Mail' to any other folder or tag
//     $path = "{imap.gmail.com:993/imap/ssl}[Gmail]/Sent Mail";
//     //Tell your server to open an IMAP connection using the same username and password as you used for SMTP
//     $imapStream = imap_open($path, $mail->Username, $mail->Password);
//     $result = imap_append($imapStream, $path, $mail->getSentMIMEMessage());
//     imap_close($imapStream);
//     return $result;
// }