Rendering HTML table with rowspan in Outlook 365 Application

How do I get this HTML rendered properly in Outlook (365) Application ?

<!DOCTYPE html>
<html>
<head>
<style style="text/css">
th {
text-align: center;
padding: 10px;
background-color: #7E9EE7;
border-color:#0A2B7E;
}
td {
text-align: center;
padding: 8px;
background-color: #DDE0E7;
border-color:#0A2B7E;
}
td:empty {
display:none;
}
tr {
text-align: center;
padding:8px;
background-color: #DDE0E7;
border-color:#0A2B7E;
}
</style>
</head>
<body>
    <table border="1" cellspacing="0" cellpadding="0" >
        <tr>
            <th>Text Heading 1</th>
            <th>Text Heading 2</th>
            <th>Text Heading 3</th>
            <th>Text Heading 4</th>
            <th>Text Heading 5</th>
            <th>Text Heading 6</th>
        </tr>
        <tr>
            <td rowspan="5">Text Content</td>
        </tr>
        <tr>
            <td rowspan="4">Text Content</td>
        </tr>
        <tr>
            <td rowspan="2">Text Content</td>
            <td>Text Content</td>
            <td>Text Content</td>
            <td rowspan="3">Text Content</td>
        </tr>
        <tr>
            <td>Text Content</td>
            <td>Text Content</td>
        </tr>
        <tr>
            <td>Text Content</td>
            <td>Text Content</td>
            <td>Text Content</td>
        </tr>
    </table>
</body>
</html>