discourse/app/assets/javascripts/admin/templates/email_preview_digest.hbs

<p>{{i18n 'admin.email.preview_digest_desc'}}</p>

<div class='admin-controls'>
  <div class='span7 controls'>
    <label for='last-seen'>{{i18n 'admin.email.last_seen_user'}}</label>
    {{input type="date" value=lastSeen id="last-seen"}}
  </div>
  <div>
    <button class='btn' {{action "refresh"}}>{{i18n 'admin.email.refresh'}}</button>
  </div>
  <div class="span7 toggle">
    <label>{{i18n 'admin.email.format'}}</label>
    {{#if showHtml}}
      <span>{{i18n 'admin.email.html'}}</span> | <a href='#' {{action "toggleShowHtml"}}>{{i18n 'admin.email.text'}}</a>
    {{else}}
      <a href='#' {{action "toggleShowHtml"}}>{{i18n 'admin.email.html'}}</a> | <span>{{i18n 'admin.email.text'}}</span>
    {{/if}}
  </div>
</div>

{{#conditional-loading-spinner condition=loading}}
  {{#if showHtml}}
    {{{html_content}}}
  {{else}}
    <pre>{{{text_content}}}</pre>
  {{/if}}
{{/conditional-loading-spinner}}