'All recipients of a message on a channel are considered as partners.
This means they will receive a minimal email, without a link to access
in the backend. Mailing lists should indeed send minimal emails to avoid
the noise.'

@api.multi
def _notification_recipients(self, message, groups):

    groups = super(Channel, self)._notification_recipients(message, groups)
    for (index, (group_name, group_func, group_data)) in enumerate(groups):
        if (group_name != 'customer'):
            groups[index] = (group_name, (lambda partner: False), group_data)
    return groups
