social/mass_mailing_newsletter_welcome_mail/data/mail_template.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2019 Tecnativa - Jairo Llopis
     License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl). -->
<data noupdate="1">

    <record id="mail_template_welcome" model="mail.template">
        <field name="name">Welcome mail to newsletter subscribers</field>
        <field name="model_id" ref="mass_mailing.model_mail_mass_mailing_contact"/>
        <field name="use_default_to" eval="True"/>
        <field name="lang">${ctx.get("lang")}</field>
        <field name="subject">Welcome to the mailing list ${ctx.get("list_name")}</field>
        <field name="body_html" type="html">
            <div>Dear <b>${object.name or object.email}</b>,
                <br/>
                <h3>Thanks for signing up for our newsletter!</h3>
                <p>Regards,</p>
            </div>
        </field>
    </record>

</data>