o365-2.0.3/modules/o365_outlook_mail/templates/o365-outlook-mail-list-block.html.twig

<div class="card__body">
  {{ list }}

  <a href="https://outlook.office.com" rel="noopener" target="_blank" class="{{ readmore_class }}">{{ 'Read more emails on Outlook.com' | t }}</a>
</div>