attachment.php

См. документацию.

<?php
 
namespace Bitrix\Mail\Integration;
 
class Attachment
{
    public static function downloadAttachmentsByMessageId(int $messageId): bool
    {
        $messageForDownload = \Bitrix\Mail\MailMessageTable::getList([
            'runtime' => [
                new \Bitrix\Main\Entity\ReferenceField(
                    'MESSAGE_UID',
                    'Bitrix\Mail\MailMessageUidTable',
                    [
                        '=this.MAILBOX_ID' => 'ref.MAILBOX_ID',
                        '=this.ID' => 'ref.MESSAGE_ID',
                    ],
                    [
                        'join_type' => 'INNER',
                    ]
                ),
            ],
            'select' => [
                '*',
                'MAILBOX_EMAIL' => 'MAILBOX.EMAIL',
                'MAILBOX_NAME' => 'MAILBOX.NAME',
                'MAILBOX_LOGIN' => 'MAILBOX.LOGIN',
                'IS_SEEN' => 'MESSAGE_UID.IS_SEEN',
                'MSG_HASH' => 'MESSAGE_UID.HEADER_MD5',
                'DIR_MD5' => 'MESSAGE_UID.DIR_MD5',
                'MSG_UID' => 'MESSAGE_UID.MSG_UID',
            ],
            'filter' => [
                '=ID' => $messageId,
            ],
            'order' => [
                'FIELD_DATE' => 'DESC',
                'MESSAGE_UID.ID' => 'DESC',
                'MESSAGE_UID.MSG_UID' => 'ASC',
            ],
            'limit' => 1,
        ])->fetch();
 
        if ($messageForDownload)
        {
            return (bool)\Bitrix\Mail\Helper\Message::ensureAttachments($messageForDownload);
        }
 
        return false;
    }
}