AWS PHP SDK v3 sendRawEmail with attachment

sendRawEmailWithAttachment.php

<?php 

use Aws\Ses\SesClient;
use Aws\Exception\AwsException;

/**
 * Send an email using the 'raw' version of the API.
 * Use this when needing to send an attachment.
 *
 * @param array $addresses
 * @param string $subject
 * @param string $message
 * @param string $sender
 * @param array $replyTo
 * @param string $attachment
 * @return array
*/
public static function sendRawEmail(
    array $addresses, 
    string $subject, 
    string $message, 
    string $sender = '[email protected]',
    array $replyTo = ['[email protected]'],
    string $attachment = ''
): array
{
    $recipients = implode(',', $addresses);

    $sesClient =  new SesClient([
        'version' => '2010-12-01',
        'region'  => 'ap-southeast-2',
        'signatureVersion' => 'v4',
        'credentials' => [
            'key' => config('aws.key'), // Replace with wherever these are fetched from
            'secret' => config('aws.secret') // Replace with wherever these are fetched from
        ]
    ]);

    try {
        $filename = basename($attachment);
        $attachedData = chunk_split(
            base64_encode(
                file_get_contents($attachment)
            )
        );  
        $mimeType = finfo_file(
            finfo_open(FILEINFO_MIME_TYPE), 
            $attachment
        );

        $separator = md5(time());
        $separatorMultipart = md5($subject . time());  

        $raw = "MIME-Version: 1.0\n";
        $raw .= "To: " . $recipients . "\n"; 
        $raw .= "From:" . $sender . "\n";   
        $raw .= "Subject:" . $subject . "\n";
        $raw .= "Content-Type: multipart/mixed; boundary=\"" . $separatorMultipart . "\"\n";
        $raw .= "\n--" . $separatorMultipart . "\n";
        $raw .= "Content-Type: multipart/alternative; boundary=\"" . $separator . "\"\n";
        $raw .= "\n--" . $separator . "\n";
        $raw .= "Content-Type: text/html; charset=\"UTF-8\"\n";
        $raw .= "\n" . $message . "\n";
        $raw .= "\n--" . $separator . "--\n";
        $raw .= "--" . $separatorMultipart . "\n";
        $raw .= "Content-Type: " . $mimeType . "; name=\"" . $filename . "\"\n";
        $raw .= "Content-Disposition: attachment; filename=\"" . $filename . "\"\n";
        $raw .= "Content-Transfer-Encoding: base64\n\n";
        $raw .= $attachedData . "\n";
        $raw .= "--" . $separatorMultipart . "--";

        $result = $sesClient->sendRawEmail([
            'Destinations' => $addresses,
            'Source' => $sender,
            'RawMessage' => [
                'Data' => $raw
            ]
        ]);

        return [
            'result' => 'success',
            'message' => $result['MessageId'] ?? 'Emails sent'
        ];
    } catch (AwsException $e) {
        error_log($e->getMessage());
        error_log('The email was not sent. Error message: ' . $e->getAwsErrorMessage());
        return [
            'result' => 'error',
            'message' => $e->getAwsErrorMessage()
        ];
    }
}