app-MAIL-temp/templates/notification/cycle-email.html

<div>
  An email was sent to your alias <b>{{ alias.email }}</b> from its own mailbox <b>{{ from_addr }}</b>.
</div>
<div>
  SimpleLogin doesn't send this email back to your mailbox as it would be refused or hidden anyway by your email
  service.
</div>
<div>
  So no worries, there's nothing you need to do :).
</div>