odoo/addons/mail/res_users_view.xml

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

        <!-- Update Preferences form !-->
        <record id="view_users_form_simple_modif_mail" model="ir.ui.view">
            <field name="name">res.users.preferences.form.mail</field>
            <field name="model">res.users</field>
            <field name="inherit_id" ref="base.view_users_form_simple_modif"/>
            <field name="arch" type="xml">
            <data>
                <xpath expr="/form/group/group[@name='preferences']/field[@name='menu_tips']" position="after">
                    <field name="notification_email_pref" readonly="0"/>
                </xpath>
            </data>
            </field>
        </record>

        <!-- Update user form !-->
        <record id="view_users_form_mail" model="ir.ui.view">
            <field name="name">res.users.form.mail</field>
            <field name="model">res.users</field>
            <field name="inherit_id" ref="base.view_users_form"/>
            <field name="arch" type="xml">
            <data>
                <xpath expr="/form/notebook/page[@string='User']/group/group/group[@name='preferences']/field[@name='menu_tips']" position="after">
                    <field name="notification_email_pref"/>
                </xpath>
                <xpath expr="/form/notebook" position="after">
                    <field name="message_ids_social" colspan="4" widget="ThreadView" nolabel="1"/>
                </xpath>
            </data>
            </field>
        </record>

    </data>
</openerp>