POP3 server backend

#!/usr/bin/env python
# -*- encoding: utf-8 -*-
"""
The auth via trust pop3 server for Django http://www.djangoproject.com
set up the trust pop3 server domain in AUTH_POP_SERVERS, you could have one or many
trusted pop3 server

require python package python-dnspython, http://www.dnspython.org/
for smart MX record lookup

ex:

AUTH_POP3_SERVERS = {'companydomain1.com':'com1','companydomain2.com':'com2'}

"""
import string
import poplib
import socket
from django.core.validators import email_re
from django.contrib.auth.models import User
import dns.resolver


# Constants
AUTH_POP3_SERVERS = {'companydomain1.com':'com1','companydomain2.com':'com2'}
BAD_USERS = ['root','bin','sys']

class POP3Backend:
    def auth_pop3_server(self,email=None,password=None):
        # find mailserver first
        domain = ''
        username = ''
        ms = '' # mail server
        if email_re.search(email):
            username = email[:email.find('@')]
            domain = email[email.find('@')+1:]

        if username and domain in AUTH_POP3_SERVERS.keys():
            # find domain name
            if username in BAD_USERS: return False
            try:
                # let's dig mx record
                a = dns.resolver.query(domain,'MX')
                for rdata in a:
                    # trim the last dot character
                    ms= rdata.exchange.to_text()[:-1]
                    try :
                        # try pop3 ssl first
                        m = poplib.POP3_SSL(ms)
                        m.user(username)
                        m.pass_(password)
                        if m.stat():
                            return True
                        else:
                            return False
                    except:
                        # pop3 ssl fail, let's try pop
                        m = poplib.POP3(ms)
                        m.user(username)
                        m.pass_(password)
                        if m.stat():
                            return True
                        else:
                            return False

                    # only try first mx record
                    break
            except:
                # some error
                return False

        return False
    def authenticate(self, username=None, password=None):
        # Authenticate the base user, the username is an email address
        # If the user does not exist in POP3 server, Fail.
 
        if not self.auth_pop3_server(email=username,password=password):
            return None

        try:
            user = User.objects.get(email=username)
        except:
            from random import choice
            temp_pass = ""
            new_user = ''
            domain = ''
            if email_re.search(username):
                domain = username[username.find('@')+1:]
                new_user = username[:username.find('@')]
                new_user = new_user + '_' +AUTH_POP3_SERVERS[domain]
                new_user = string.lower(new_user)
            for i in range(8):
                temp_pass = temp_pass + choice(string.letters)
            user = User.objects.create_user(new_user,username,temp_pass)
            user.is_staff = False
            user.save()

        # Success.
        return user

    def get_user(self, user_id):
        try:
            return User.objects.get(pk=user_id)
        except User.DoesNotExist:
            return None