From Cerberus mail : http://tedgoas.github.io/Cerberus/

newsletter_two-columns.html

 <!-- Progressive Enhancements -->
<style>
    /* Media Queries */
    @media screen and (max-width: 480px) {

        /* What it does: Forces table cells into full-width rows. */
        .stack-column {
            display: block !important;
            width: 100% !important;
            max-width: 100% !important;
            direction: ltr !important;
        }

    }
</style>

<!-- Two Even Columns : BEGIN -->
<tr>
    <td bgcolor="#ffffff" align="center" height="100%" valign="top" width="100%">
        <!--[if mso]>
        <table border="0" cellspacing="0" cellpadding="0" align="center" width="660">
        <tr>
        <td align="center" valign="top" width="660">
        <![endif]-->
        <table border="0" cellpadding="0" cellspacing="0" align="center" width="100%" style="max-width:660px;">
            <tr>
                <td align="center" valign="top" style="font-size:0; padding: 10px 0;">
                    <!--[if mso]>
                    <table border="0" cellspacing="0" cellpadding="0" align="center" width="660">
                    <tr>
                    <td align="left" valign="top" width="330">
                    <![endif]-->
                    <div style="display:inline-block; margin: 0 -2px; width:100%; min-width:200px; max-width:330px; vertical-align:top;" class="stack-column">
                        <table cellspacing="0" cellpadding="0" border="0" width="100%">
                            <tr>
                                <td style="padding: 10px 10px;">
                                    <table cellspacing="0" cellpadding="0" border="0" width="100%" style="font-size: 14px;text-align: left;">
                                        <tr>
                                            <td>
                                                <img src="http://placehold.it/310" width="310" alt="" style="border: 0;width: 100%;max-width: 310px;" class="center-on-narrow">
                                            </td>
                                        </tr>
                                        <tr>
                                            <td style="font-family: sans-serif; font-size: 15px; mso-height-rule: exactly; line-height: 20px; color: #555555; padding-top: 10px;" class="stack-column-center">
                                                Maecenas sed ante pellentesque, posuere leo id, eleifend dolor. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. 
                                            </td>
                                        </tr>
                                    </table>
                                </td>
                            </tr>
                        </table>
                    </div>
                    <!--[if mso]>
                    </td>
                    <td align="left" valign="top" width="330">
                    <![endif]-->
                    <div style="display:inline-block; Margin: 0 -2px; width:100%; min-width:200px; max-width:330px; vertical-align:top;" class="stack-column">
                        <table width="100%">
                            <tr>
                                <td style="padding: 10px 10px;">
                                    <table cellspacing="0" cellpadding="0" border="0" width="100%" style="font-size: 14px;text-align: left;">
                                        <tr>
                                            <td>
                                                <img src="http://placehold.it/310" width="310" alt="" style="border: 0;width: 100%;max-width: 310px;" class="center-on-narrow">
                                            </td>
                                        </tr>
                                        <tr>
                                            <td style="font-family: sans-serif; font-size: 15px; mso-height-rule: exactly; line-height: 20px; color: #555555; padding-top: 10px;" class="stack-column-center">
                                                Maecenas sed ante pellentesque, posuere leo id, eleifend dolor. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. 
                                            </td>
                                        </tr>
                                    </table>
                                </td>
                            </tr>
                        </table>
                    </div>
                    <!--[if mso]>
                    </td>
                    </tr>
                    </table>
                    <![endif]-->
                </td>
            </tr>
        </table>
        <!--[if mso]>
        </td>
        </tr>
        </table>
        <![endif]-->
    </td>
</tr>
<!-- Two Even Columns : END -->