social/mail_tracking_mailgun/views/res_partner.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2016 Tecnativa - Pedro M. Baeza
     Copyright 2016 Carlos Dauden - Tecnativa <carlos.dauden@tecnativa.com>
     Copyright 2017 Tecnativa <vicent.cubellsn@tecnativa.com>
     License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html). -->
<odoo>

    <record id="view_partner_form_mailgun" model="ir.ui.view">
        <field name="name">Partner Mailgun button</field>
        <field name="model">res.partner</field>
        <field name="inherit_id" ref="mail_tracking.view_partner_form"/>
        <field name="arch" type="xml">
            <field name="email_bounced" position="after">
                <label for="check_email_bounced" string="Mailgun"
                       attrs="{'invisible': [('email', '=', False)]}"/>
                <div name="mailgun_buttons" attrs="{'invisible': [('email', '=', False)]}">
                    <button name="check_email_bounced" type="object" string="Check Mailgun" class="oe_link"/>
                    <button name="check_email_validity" type="object" string="Check email validity" class="oe_link"/>
                    <button name="force_set_bounced" type="object" string="Set Bounced" class="oe_link"
                            attrs="{'invisible': [('email_bounced', '=', True)]}"/>
                    <button name="force_unset_bounced" type="object" string="Unset Bounced" class="oe_link"
                            attrs="{'invisible': [('email_bounced', '=', False)]}"/>
                </div>
            </field>
        </field>
    </record>

</odoo>