mail-addons/mail_private/view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <record id="mail_private_email_compose_message_wizard_form" model="ir.ui.view">
            <field name="name">mail.private.mail.compose.message.form</field>
            <field name="model">mail.compose.message</field>
            <field name="inherit_id" ref="mail.email_compose_message_wizard_form"/>
            <field name="arch" type="xml">
                <xpath expr="//div[@groups='base.group_user']" position="replace">
                    <div groups="base.group_user" attrs="{'invisible': [('is_log', '=', True)]}">
                        <field name="private" invisible="1"/>
                        <!--<field name="private"/>-->
                        <span attrs="{'invisible': [('composition_mode', '!=', 'mass_mail')]}">
                            <strong>Email mass mailing</strong> on
                            <span attrs="{'invisible': [('use_active_domain', '=', True)]}">the selected records</span>
                            <span attrs="{'invisible': [('use_active_domain', '=', False)]}">the current search filter</span>.
                        </span>
                        <span attrs="{'invisible':['|', ('composition_mode', '!=', 'comment'), ('private', '=', True)]}">Followers of the document and</span>
                        <field name="partner_ids" widget="many2many_tags_email" placeholder="Add contacts to notify..."
                            context="{'force_email':True, 'show_email':True}"
                            attrs="{'invisible': [('composition_mode', '!=', 'comment')]}"/>
                    </div>
                </xpath>
            </field>
        </record>
    </data>
</openerp>