Use this :
<div style="width:700px; background:#F2F2F2">
<table style="width:100%;padding: 25px; margin: 0 auto; font-family:'Open Sans', 'Helvetica', 'Arial';">
<tr align="center" style="margin: 0; padding: 0;">
<td>
<table style="width:100%;border-style:solid; border-width:2px; border-color: #c3d2d9;" cellspacing="0">
<tr style="background-color: white;">
<td style=" padding: 10px 15px 10px 15px; color: #000000;">
<p>Some content here</p>
<span style="font-weight: bold;">My Signature</span><br/>
My Title<br/>
My Company<br/>
</td>
</tr>
</table>
</td>
</tr>
</table>
</div>