etc/module.xml
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
<module name="Staempfli_MailCatcher" setup_version="0.0.1" >
<sequence>
<module name="Magento_Email"/>
</sequence>
</module>
</config>