odoo16/addons/mass_mailing/views/mailing_templates_portal_unsubscribe.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <template id="unsubscribe">
        <div class="container o_unsubscribe_form">
            <div class="row">
                <form action="/mail/mailing/unsubscribe" method="POST" id="unsubscribe_form" class="col-lg-6 offset-lg-3 mt-4">
                    <input type="hidden" name="csrf_token" t-att-value="request.csrf_token()"/>
                    <input type="hidden" name="email" t-att-value="email"/>
                    <input type="hidden" name="mailing_id" t-att-value="mailing_id"/>
                    <input type="hidden" name="res_id" t-att-value="res_id"/>
                    <input type="hidden" name="unsubscribed_list" t-att-value="unsubscribed_list"/>

                    <div>
                        <t t-if="contacts">
                            <div id="info_state" class="alert alert-success" role="status">
                                <div id="subscription_info"></div>
                                <div id="div_feedback">
                                    <p>We would appreciate if you provide feedback about why you updated<br/>your subscriptions</p>
                                    <textarea class="form-control"  name="opt_out_feedback" cols="60" rows="3"></textarea>
                                    <br/>
                                    <div class="btn btn-primary text-start" id="button_feedback">Send</div>
                                </div>
                            </div>

                            <h1 class="o_page_header">Mailing Subscriptions</h1>
                            <p>Choose your mailing subscriptions</p>
                            <div id="div_opt_out">
                                <ul class="list-group">
                                    <t t-foreach="list_ids" t-as="list_id">
                                        <t t-if="list_id.is_public == True">
                                            <li class="list-group-item">
                                                <input type="checkbox" name="contact_ids"
                                                    t-att-value="list_id['id']" t-att-checked="None if list_id['id'] in opt_out_list_ids else 'checked'"/>
                                                <t t-esc="list_id.name"/>
                                                <span t-if="list_id['id'] in opt_out_list_ids"
                                                      class="o_mailing_portal_list_unsubscribed">
                                                    Unsubscribed
                                                </span>
                                            </li>
                                        </t>
                                    </t>
                                </ul>

                                <div class="mb64 pt-3">
                                    <div class="btn btn-link float-end pe-0 text-uppercase"
                                         t-if="show_blacklist_button"
                                         id="button_add_blacklist"
                                         style="display:none">Blacklist Me</div>
                                    <div class="btn btn-link float-end pe-0 text-uppercase"
                                         id="button_remove_blacklist"
                                         style="display:none">Come Back</div>
                                    <button type="submit" id="send_form"
                                            class="btn btn-primary">Update my subscriptions</button>
                                </div>
                            </div>

                        </t>
                        <t t-else="">
                            <div class="alert alert-info text-center" role="status">
                                <p>You are not subscribed to any of our mailing list.</p>
                            </div>
                        </t>
                    </div>
                </form>
            </div>
        </div>
    </template>

    <template id="unsubscribed">
        <div class="container o_unsubscribe_form">
            <div class="row">
                <input type="hidden" name="email" t-att-value="email"/>
                <input type="hidden" name="mailing_id" t-att-value="mailing_id"/>
                <input type="hidden" name="res_id" t-att-value="res_id"/>
                <div id="div_blacklist" class="col-lg-6 offset-lg-3">
                    <h1 class="o_page_header">Mailing Subscriptions</h1>

                    <div id="subscription_info" class="alert alert-success text-center" role="status">
                        <p>You have been successfully <strong>unsubscribed</strong>!</p>
                    </div>

                    <div t-if="list_ids" class="alert alert-warning">
                        <p class="text-center">You were still subscribed to those newsletters. You will not receive any news from them anymore:</p>
                        <ul class="list-group mb-4">
                            <t t-foreach="list_ids" t-as="list_id">
                                <t t-if="list_id.is_public == True">
                                    <li class="list-group-item bg-transparent">
                                        <strong><t t-esc="list_id.name"/></strong>
                                    </li>
                                </t>
                            </t>
                        </ul>
                    </div>

                    <div t-if="show_blacklist_button" class="mb64">
                        <div class="btn btn-link float-end"
                             id="button_add_blacklist"
                             style="display:none">Blacklist Me</div>
                        <div class="btn btn-link float-end"
                             id="button_remove_blacklist"
                             style="display:none">Come Back</div>
                    </div>
                </div>
            </div>
        </div>
    </template>

    <template id="page_unsubscribe" name="Unsubscribe">
        <t t-call="mass_mailing.layout">
            <t t-call="mass_mailing.unsubscribe"/>
        </t>
    </template>

    <template id="page_unsubscribed" name="Unsubscribed">
        <t t-call="mass_mailing.layout">
            <t t-call="mass_mailing.unsubscribed"/>
        </t>
    </template>
</odoo>