app/templates/notification/message-quarantine.html

<div>
  An email from {{ from_header }} to {{ alias.email }} is put into Quarantine as it fails DMARC check.
  <br>
  <a href="https://en.wikipedia.org/wiki/DMARC">DMARC</a> is an email authentication protocol designed for detecting
  phishing. When an email fails DMARC, it can be considered as suspicious.
</div>

<a href="/dashboard/refused_email" class="btn btn-primary">
  View quarantined emails
</a>

<div>
  The email is automatically deleted in 7 days.
</div>