How to delete mail in macOS Mojave’s Mail app
<p style="white-space: pre-wrap;">There are several ways to delete mail in the Mail app of macOS Mojave. To delete a message from a Mail notification or with a swipe, the “Move discarded messages” option in <a href="https://support.apple.com/guide/mail/viewing-preferences-cpmlprefview" target="_blank" rel="noopener noreferrer">Viewing preferences</a> in Mail must be set to Trash; otherwise, the message is archived.</p>