使用Amazon SES发送电子邮件时出错

My Email sending script was working fine for the last few years.

Few days back I saw following error message when I ran email sending script:

I am not getting why this is happening when I send email using Amazon SES, earlier it never happened.

Here is email sending script code :

    <?php
ob_start();
ini_set('memory_limit', '512M');
ECHO $document_root =   $_SERVER['DOCUMENT_ROOT'];;
require_once($document_root."wp-load.php");


function testnewcronsendmail()
{
    $mail = new PHPMailer;
    $mail->From = 'info@itsxxx.com'; // A Verified email.
    $mail->FromName = 'MYSON';

    //$mail->addAddress('ravikathait01@gmail.com');   
    $mail->addAddress('shishupal.shakya@itsxxx.com');

    $mail->isHTML(true);  

    $mail->Subject = 'test' ;
    $mail->Body    = 'test';
    var_dump($mail->ErrorInfo);
    var_dump($mail->send());
}

testnewcronsendmail();

?>

I did some learning and found that it is server related issue but I am not getting which thing should I correct at the server.

Anyone who faced such issue earlier, Pls suggest me the solution.