Content was already there in the mail, but make it clear to the user
what it looks like.
<form method="post" action=".">{%csrf_token%}
<table class="sendmailform">
+<tr>
+ <th>Sender</th>
+ <td>{{conference.conferencename}} <{{conference.contactaddr}}></td>
{{form}}
+<tr>
+ <th>Suffix</th>
+ <td>The email will contain a suffix with a link to {{sitebase}}/events/{{conference.urlname}}/register/signup/{{signup.id}}/</td>
+</tr>
</table>
<input type="submit" value="Send mail" class="btn btn-default">
</form>