bemade-addons/bemade_mailcow_blacklist/views/mailcow_mailbox_views.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <record id="view_mailcow_mailbox_tree" model="ir.ui.view">
        <field name="name">mailcow.mailbox.view.tree</field>
        <field name="model">mail.mailcow.mailbox</field>
        <field name="arch" type="xml">
            <tree string="Mailbox" decoration-info="active == False" js_class="mail_mailcow_mailbox_tree"> <!-- js_class must match the name added to the viewRegistry in js -->
                <field name="active"/>
                <field name="name"/>
                <field name="local_part"/>
                <field name="domain"/>
                <field name="address"/>
                <field name="user_id"/>
            </tree>
        </field>
    </record>

    <record id="mailcow_mailbox_view_form" model="ir.ui.view">
        <field name="name">mailcow.mailbox.view.form</field>
        <field name="model">mail.mailcow.mailbox</field>
        <field name="arch" type="xml">
            <form string="Mailbox">
                <sheet>
                    <group>
                        <field name="active"/>
                        <field name="name"/>
                        <field name="local_part"/>
                        <field name="domain"/>
                        <field name="address"/>
                        <field name="user_id"/>
                    </group>
                    <notebook>
                        <page string="Messages" name="messages">
                            <field name="message_ids" widget="mail_thread"/>
                        </page>
                    </notebook>
                </sheet>
            </form>
        </field>
    </record>

    <record id="action_mailcow_mailbox" model="ir.actions.act_window">
        <field name="name">Mailboxes</field>
        <field name="type">ir.actions.act_window</field>
        <field name="res_model">mail.mailcow.mailbox</field>
        <field name="view_mode">tree,form</field>
        <field name="help" type="html">
            <p class="o_view_nocontent_smiling_face">
                Create a new Mailbox
            </p>
            <p>
                Add the details of the new Mailbox.
            </p>
        </field>
    </record>

    <menuitem id="mailcow_menu"
              name="Mailcow"
              sequence="10"
              web_icon="bemade_mailcow_blacklist,static/description/icon.png"/>

    <menuitem id="mailcow_menu_mailbox"
              name="Mailboxes"
              parent="mailcow_menu"
              action="action_mailcow_mailbox"
              sequence="10"/>

    <record id="action_server_sync_mailboxes" model="ir.actions.server">
        <field name="name">Sync Mailboxes</field>
        <field name="model_id" ref="model_mail_mailcow_mailbox"/>
        <field name="state">code</field>
        <field name="code">model.sync_mailboxes()</field>
    </record>

    <record id="action_sync_mailboxes" model="ir.actions.act_window.view">
        <field name="sequence" eval="10"/>
        <field name="view_mode">tree</field>
        <field name="act_window_id" ref="action_mailcow_mailbox"/>
        <field name="view_id" ref="view_mailcow_mailbox_tree"/>
    </record>

</odoo>