'Forge the email_to with the following heuristic:
- if \'partner\', recipient specific (Partner Name <email>)
- else fallback on mail.email_to splitting'

@api.multi
def send_get_mail_to(self, partner=None):

    self.ensure_one()
    if partner:
        email_to = [formataddr((partner.name, partner.email))]
    else:
        email_to = tools.email_split_and_format(self.email_to)
    return email_to
