data-protection/privacy_consent/data/ir_actions_server.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2018 Tecnativa - Jairo Llopis
     Copyright 2019 initOS GmbH - Florian Kantelberg
     License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl). -->

<data>

    <record id="sync_blacklist" model="ir.actions.server">
        <field name="name">Sync partner's email blacklist status</field>
        <field name="model_id" ref="model_privacy_consent"/>
        <field name="crud_model_id" ref="base.model_res_partner"/>
        <field name="state">code</field>
        <field name="code">
            for consent in records:
                email = consent.partner_id.email
                # Skip records without email, although highly improbable
                if not email:
                    continue
                # Choose method to sync acceptance and blacklisting
                if consent.accepted:
                    method = env["mail.blacklist"]._remove
                else:
                    method = env["mail.blacklist"]._add
                # Apply user desire
                method(email)
        </field>
    </record>

</data>