discourse/app/views/user_notifications/digest.html.erb

<table style="border: 20px solid #eee;" cellspacing="0" cellpadding="0">
<tr>
  <td style="padding: 10px 10px; background-color: #<%= @header_color %>;">
    <a href="<%= Discourse.base_url %>">
    <%- if logo_url.blank? %>
      <%= SiteSetting.title %>
    <%- else %>
      <img src="<%= logo_url %>" style="max-height: 35px; min-height: 35px; height: 35px;" class='site-logo'></a>
    <%- end %>
  </td>
</tr>
<tr>
  <td style="background-color: #fff; padding: 10px 10px; font-family: Arial, Helvetica, sans-serif; font-size: 14px;">
    <%= raw(t 'user_notifications.digest.why', site_link: html_site_link, last_seen_at: @last_seen_at) %>

    <%- if @featured_topics.present? %>
      <hr/>
      <h3><%=t 'user_notifications.digest.top_topics' %></h3>


      <%- @featured_topics.each_with_index do |t, i| %>
        <div class='featured-topic'>
          <%= link_to t.title, "#{Discourse.base_url}#{t.relative_url}" %>
          <br/>
          <%= category_badge(t.category, inline_style: true, absolute_url: true) %>
        </div>

        <%- if t.best_post.present? %>
          <div class='digest-post'>
            <%= email_excerpt(t.best_post.cooked, @featured_topics.size) %>
          </div>
        <%- end %>

        <%- if i < @featured_topics.size - 1 %><% end %>

      <%- end %>
    <%- end %>

    <%- if @new_topics.present? %>
      <hr/>
      <h3><%=t 'user_notifications.digest.other_new_topics' %></h3>

      <%- @new_topics.each do |t| %>
        <ul>
          <li>
            <%= link_to t.title, "#{Discourse.base_url}#{t.relative_url}" %>
            <span class='post-count'><%= t.posts_count %></span>
            <%= category_badge(t.category, inline_style: true, absolute_url: true) %>
          </li>
        </ul>
      <%- end -%>

    <%- end -%>

    <%- if @new_topics_since_seen > 0 %>
      <%- if @new_by_category.present? %>
        <p><%= t('user_notifications.digest.more_topics_category', last_seen_at: @last_seen_at, new_topics_since_seen: @new_topics_since_seen) %></p>
        <div>
        <%- @new_by_category.first(10).each do |c| %>
          <span style='white-space: nowrap'>
            <a href='<%= Discourse.base_url %><%= c[0].url %>' style='color: #333'><%= c[0].name %></b> <span style='color: #777; margin: 0 10px 0 5px; font-size: 0.9em;'> <%= c[1] %></span>
          </span>
        <%- end %>
      </div>
      <%- else %>
        <p><%= t('user_notifications.digest.more_topics', last_seen_at: @last_seen_at, new_topics_since_seen: @new_topics_since_seen) %></p>
      <%- end %>
    <%- end -%>
  </td>
</tr>
</table>

<div class='footer'>
  <%=raw(t :'user_notifications.digest.unsubscribe',
           site_link: html_site_link,
           unsubscribe_link: link_to(t('user_notifications.digest.click_here'), email_unsubscribe_url(host: Discourse.base_url, key: @unsubscribe_key)))  %>
</div>