ขอสอบถาม PHPMailer ซึ่งก่อนหน้านี้สามารถใช้งานได้ปกติ วันนี้แสดง Error ไม่สามารถส่งได้

{	
	$strTo = $mail_user;
	$strSubject = "=?UTF-8?B?".base64_encode("ระบบแจ้งงานแผนก IT :".$code."")."?=";
	$strHeader .= "MIME-Version: 1.0' . \r\n";
	$strHeader .= "Content-type: text/html; charset=utf-8\r\n"; 
	$strMessage = "เรื่องผลการซ่อม\n<br>เรียนคุณ ".$user_name." ".$user_lname."
					\n<br>รหัสงาน :".$code."\n\n<br>ปัญหา : ".$job_detail."
					\n<br>สถานะ : Complete	
					";
	
	$mail = new PHPMailer;
	$mail->CharSet = "utf-8";
	$mail->From = "[email protected]";
	$mail->FromName = "IT Helpdesk";
	$mail->isSMTP();                                      // Set mailer to use SMTP
	$mail->Host = 'mail.thailand.com';  // Specify main and backup SMTP servers
	$mail->SMTPAuth = true;                               // Enable SMTP authentication
	$mail->Username = '[email protected]';                 // SMTP username
	$mail->Password = '1234';                           // SMTP password
	$mail->SMTPSecure = 'tls';                            // Enable TLS encryption, `ssl` also accepted
	$mail->Port = 25; 

	//To address and name
	$mail->AddAddress($mail_user);			
	$mail->AddCC('[email protected]');

	
	//Send HTML or Plain Text email
	$mail->isHTML(true);
	$mail->Subject = $strSubject;
	$mail->Body = $strMessage;			
	
	
	
//	$flgSend = mail($strTo,$strSubject,$strMessage,$strHeader);  // @ = No Show Error //
		if(!$mail->send()) 
				{
					echo "Mailer Error: " . $mail->ErrorInfo;
				} 
				else 
				{
					echo "Message has been sent successfully";
				}

	}