Separate out "not sent yet" from "not supposed to be sent yet".
</tr>
{%for m in mails%}
<tr>
- <td>{{m.sentat|date:"Y-m-d H:i"}}{%if m.future%} (Not sent yet!){%endif%}</td>
+ <td>{{m.sentat|date:"Y-m-d H:i"}}{%if m.future%} (Not scheduled yet!){%elif not m.sent%} (Not sent yet){%endif%}</td>
<td><a href="{{m.id}}/">{{m.subject}}</a></td>
<td><ul class="nopad">{%for rc in m.regclasses.all %}<li>{{rc}}</li>{%endfor%}</ul></td>
<td><ul class="nopad">{%for ao in m.addopts.all %}<li>{{ao.name}}</li>{%endfor%}</ul></td>