<?php

use Bitrix\Main;

$eventManager = Main\EventManager::getInstance();
$eventManager->addEventHandler('main', 'OnBeforeMailSend', static function (Main\Event $event) {
    $arMailParams = $event->getParameter(0);
    $arMailParams['HEADER']['FROM'] = 'no-reply@' . $_SERVER['SERVER_NAME'];

    $event->addResult(new Main\EventResult(Main\EventResult::SUCCESS, $arMailParams));
});