I use this trick:
<table>
<tr style="border-bottom:1px solid black">
<td colspan="100%"></td>
</tr>
<tr> ... </tr>
</table>
I use this trick:
<table>
<tr style="border-bottom:1px solid black">
<td colspan="100%"></td>
</tr>
<tr> ... </tr>
</table>