This page discusses using tables for layout in HTML emails, including nested tables.
Many email clients have limited CSS support, making it challenging to use modern layout techniques like flexbox or grid. Tables provide a reliable way to structure email content for consistent rendering across different clients.
<table>
<tr>
<td>Cell 1</td>
<td>Cell 2</td>
</tr>
</table>
<table>
<tr>
<td>
<table>
<tr>
<td>Nested Cell</td>
</tr>
</table>
</td>
</tr>
</table>
cellpadding, cellspacing, and border to 0 unless needed.