Impacted versions:

8.0

Steps to reproduce:

To reproduce this one, you have to configure outgoing and incoming server and mail aliases

see https://youtu.be/-HzDGh9C9Jc

Current behavior:

If you add a user which has no acces on a object (purchase.order in this case) as follower on a record of this object **AFTER someone has responded by email on this record**, and if you send an message on this record, an exception is raised at the connection of the user added as a follower.

Expected behavior:

No exceptions should be raised at the connection of the user added as a follower.

Video/Screenshot link (optional):

https://youtu.be/-HzDGh9C9Jc

max_length = 300
            else:
                max_length = 100
            body_short = html_email_clean(message.body, remove=False, shorten=True, max_length=max_length)
        except Exception:
            body_short = '<p><b>Encoding Error : </b><br/>Unable to convert this message (id: %s).</p>' % message.id
            _logger.exception(Exception)
        return {'id': message.id,
                'type': message.type,
                'subtype': message.subtype_id.name if message.subtype_id else False,
                'body': message.body,
                'body_short': body_short,
                'model': message.model,
                'res_id': message.res_id,
                'record_name': message.record_name,
                'subject': message.subject,
                'date': message.date,
                'to_read': message.to_read,
                'parent_id': parent_id,
                'is_private': is_private,
                'author_id': False,
                'author_avatar': message.author_avatar,
                'is_author': False,
                'partner_ids': [],
                'vote_nb': vote_nb,
                'has_voted': has_voted,
                'is_favorite': message.starred,
                'attachment_ids': [],
            }
    def _message_read_add_expandables(self, cr, uid, messages, message_tree, parent_tree,