magento-test/app/code/Magento/Quote/etc/frontend/events.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="sales_model_service_quote_submit_success">
        <observer name="sendEmail" instance="Magento\Quote\Observer\SubmitObserver"/>
        <observer name="sendInvoiceEmail" instance="Magento\Quote\Observer\SendInvoiceEmailObserver"/>
    </event>
</config>