mail-addons/mail_check_immediately/static/src/xml/main.xml

<?xml version="1.0" encoding="utf-8"?>
<templates>
    <t t-name="fetch_mail_immediately.header">
        <tr class="oe_header_row">
            <td t-att-colspan="colspan or '3'">
                <div class="oe_view_manager_fetch_mail_imm">
                    <em>
                    <span>Mails fetched:</span>
                    <a href="#" class="oe_fetch_new_mails" title="Click to fetch mails now">
                    <span class="oe_view_manager_fetch_mail_imm_field"></span>
                    </a>
                    </em>
                </div>
            </td>
            <td></td>
        </tr>
    </t>
    <t t-extend="mail.wall">
        <t t-jquery="tr.oe_header_row_top" t-operation="after">
            <t t-call="fetch_mail_immediately.header">
                <t t-set="colspan" t-value="2"/>
            </t>
        </t>
    </t>
</templates>