Smtplib отправка писем с использованием сквозной windows-авторизации

#!c:/python27/python.exe
# -*- coding: utf-8 -*-
 
import smtplib
from email.utils import formataddr
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart
from email.mime.image import MIMEImage
 
mail_text = "Text"
mail_host = "host"
addresses = ['my_address@domain.ru']
full_message = MIMEMultipart()
mail_message = MIMEText(mail_text, 'html', 'cp1251')
full_message['Subject'] = 'Subj'.format(sys_type.decode('cp1251'))
full_message['From'] = 'my_address@domain.ru'
full_message.set_unixfrom(mail_address)
full_message.set_charset('cp1251')
full_message.attach(mail_message)
for img_file in images:
    full_message.attach(image)
server = smtplib.SMTP(mail_host, 587)
server.starttls()
server.login('domen\MyName', 'Pass')
for to_address in addresses:
    full_message['To'] = formataddr((to_address, to_address))
    print "<p>{}</p>".format(full_message)
    server.sendmail(mail_address, to_address, full_message.as_string())
server.quit()

server = smtplib.SMTP(mail_host, 587) # вместо server = smtplib.SMTP(mail_host)
server.starttls()
server.login('domen\MyName', 'Pass')