app/views/mailer/direct_message_for_sender.html.erb
<td style="<%= css_for_mailer_content %>">
<h1 style="<%= css_for_mailer_heading %>">
<%= t("mailers.direct_message_for_sender.title") %>
</h1>
<p style="<%= css_for_mailer_text %>">
<%= sanitize(t("mailers.direct_message_for_sender.text", receiver: @direct_message.receiver.name)) %>
</p>
<p style="<%= css_for_mailer_text %>">
<%= @direct_message.title %>
</p>
<div style="<%= css_for_mailer_text %>">
<%= mailer_simple_format(@direct_message.body) %>
</div>
</td>