mail-addons/mass_mailing_extra/views.xml

<?xml version="1.0"?>
<openerp>
    <data>

        <record model="ir.ui.view" id="view_mail_mail_statistics_form">
            <field name="name">mail.mail.statistics.form</field>
            <field name="model">mail.mail.statistics</field>
			<field name="inherit_id" ref="mass_mailing.view_mail_mail_statistics_form"/>
            <field name="arch" type="xml">
				<xpath expr="//form" position="inside">
					<notebook>
						<page string="Partners">
							<group>
								<label for="partners" string="Partners (summary)"/>
								<field name="partners" readonly="1" nolabel="1"/>
								<field name="partner_id" readonly="1"/>
							</group>
							<label for="partner_ids"/>
							<field name="partner_ids" readonly="1"/>
						</page>
					</notebook>
				</xpath>
			</field>
		</record>

        <record model="ir.ui.view" id="view_mail_mail_statistics_tree">
            <field name="name">mail.mail.statistics.tree</field>
            <field name="model">mail.mail.statistics</field>
			<field name="inherit_id" ref="mass_mailing.view_mail_mail_statistics_tree"/>
            <field name="arch" type="xml">
				<xpath expr="//field[@name='mail_mail_id_int']" position="before">
					<field name="partners"/>
				</xpath>
            </field>
        </record>

	</data>
</openerp>