Integration of Amazon SES SDK

I've built a simple plugin to integrate Amazon SES SDK, but it does not work.

example.com/members/mod/amazon/start.php

<?php


elgg_register_event_handler('init', 'system', 'amazon_ses_init');


function amazon_ses_init() {


   elgg_register_plugin_hook_handler('email', 'system', function($hook, $type, $returnvalue, $params)     {

        if ($returnvalue === true) {

            return;

        }


    $to_address = '';

$contact = $returnvalue['to'];

$containsName = preg_match('/<(.*)>/', $contact, $matches) == 1;

if ($containsName) {

$to_address = $matches[1];

} else {

$to_address = $contact;

}

if (!$to_address) {

return $returnvalue;

}

$users = get_user_by_email($to_address);

$recipient = $users[0];


if (!($recipient instanceof ElggUser)) {

return $returnvalue;

}

$message = $returnvalue['body'];

    $subject = $returnvalue['subject'];

    $from = $returnvalue['from'];

   

    /** ==========AMAZON SES (comment/uncomment) ====================== */

    include_once(dirname(__FILE__) . '/functions/amazonSes.php');

    mailAmazonSES($to_address,$from,$subject,$message);


    /** ==========mail PHP  (uncomment/comment)====================== */

    /*$headers = "From: $from";

    mail($to_address,$subject,$message,$headers);*/


   return true;

  });

}
 
<?php

use Aws\Ses\SesClient;

use Aws\Ses\Exception\SesException;


function mailAmazonSES($to,$from,$subject,$textMSG) {

    include_once './Amazon-AWS-SDK/aws-autoloader.php';


    $client = SesClient::factory(array(

        'version'=> 'latest',     

        'region' => 'us-east-1'

    ));

    $charset = 'UTF-8';

    try {

        $result = $client->sendEmail([

        'Destination' => [

            'ToAddresses' => [

                $to,

            ],

        ],

        'Message' => [

            'Body' => [

'Text' => [

                    'Charset' => $charset,

                    'Data' => $textMSG,

                ],

            ],

            'Subject' => [

                'Charset' => $charset,

                'Data' => $subject,

            ],

        ],

    'Source' => $from, 

  ]);

     $messageId = $result->get('MessageId');

     //echo("Email sent! Message ID: $messageId"."\n");


    } catch (SesException $error) {

        //echo("The email was not sent. Error message: ".$error->getAwsErrorMessage()."\n");

    }

}
 
<?php
include_once(dirname(__FILE__) . '/functions/amazonSes.php');
    $from = 'noreply@example.com';
    $to_address = 'zelinkovsky@gmail.com';
    $subject = "My Test Subject";
    $textMSG = "Dear Text Friend,\r\nThis email was send with Amazon SES using the AWS SDK for PHP";
   
     mailAmazonSES($to_address,$from,$subject,$textMSG);
 ?>

It works well when I try to call the SDK directly through example.com/members/mod/amazon/amazon-test.php

When I try the start.php with mail php (see at the bottom of start.php) it works well.

However, it does not work when I try start.php with the function mailAmazonSES 

Please advise

Thank you