plugins/send_email/views/send_email_plugin/success.html.erb
<h2><%= _('Message sent') %></h2>
<table class='sendemail-plugin-message-sent'>
<tr><td class='label'><strong><%= c_('Subject') %>:</strong></td><td class='value'><em><%=h @mail.subject %></em></td></tr>
<tr><td class='label'><strong><%= c_('Message') %>:</strong></td><td class='value'><pre><%=h render :file => 'send_email_plugin/sender/send_message' %></pre></td></tr>
</table>
<p><%= button :back, c_('Back'), :back %></p>