appwrite/app/config/locale/templates/email-cta.tpl

<table role="presentation" border="0" cellpadding="0" cellspacing="0" class="btn btn-primary">
  <tbody>
    <tr>
      <td>
        <table role="presentation" border="0" cellpadding="0" cellspacing="0">
          <tbody>
            <tr>
              <td>
                <a href="{{redirect}}" target="_blank">
                  {{title}}
                </a>
              </td>
            </tr>
          </tbody>
        </table>
      </td>
    </tr>
  </tbody>
</table>
<p>
  <a href="{{redirect}}" target="_blank">
    {{redirect}}
  </a>
</p>