Hi Marcus,

Yes, this can be done with a custom module.

You can override the email sending method and convert the HTML body to plain text before it's sent. One way is to strip out HTML tags from body_html like this:

from odoo import models

import re

class MailMail(models.Model):

    _inherit = 'mail.mail'

    def _send(self, auto_commit=False, raise_exception=False):

        if self.body_html:

            self.body_html = re.sub('<[^<]+?>', '', self.body_html)

        return super()._send(auto_commit=auto_commit, raise_exception=raise_exception)

This will force outgoing emails to plain text. It's basic, but should reduce clutter from HTML replies and footers.