<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <record model="ir.ui.view" id="email_compose_message_wizard_inherit_form">
        <field name="name">mail.compose.message.form (mail_optional_autofollow)</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[field[@name='partner_ids']]" position="after">
                <field name="autofollow_recipients" />
            </xpath>
        </field>
    </record>
</odoo>
<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <record model="ir.ui.view" id="email_compose_message_wizard_inherit_form">
        <field name="name">mail.compose.message.form (mail_optional_autofollow)</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[field[@name='partner_ids']]" position="after">
                <field name="autofollow_recipients" attrs="{'invisible': [('composition_mode', '=', 'mass_mail')]}"/>
            </xpath>
        </field>
    </record>
</odoo>
Hide the checkbox for the mass mailing in mail_optional_autofollow
[IMP] Hide the checkbox for the mass mailing in mail_optional_autofollow
