Requirements:
    - python 2.3.x or later (http://www.python.org/)
    - the python milter module (http://www.bmsi.com/python/milter.html)
    - the PyDNS module (http://pydns.sourceforge.net/)
    - sendmail with milter support

Installation:
    - put the two python files in a convenient location
    - decide where to put the milter socket. It needs to be somewhere where 
    the milter script has write access (don't run it as root!) and sendmail 
    can access it. Don't put it in a world writable directory or sendmail 
    will complain
    - add the following line to your sendmail.mc:

INPUT_MAIL_FILTER(`siqfilter', `S=local:/path/to/milter/socket')dnl

    (replace the socket file location with the location you picked)

    - arrange for siqmilter.py to be run on startup and supply the socket
    file location on the command line

Notes:
    - logging is done to stdout so redirect it to a file / use daemontools or
    something else if you want to keep the logs
    - by default, the milter will never reject mail even if it's unauthorized.
    If you want it to do so, you need to use -r flag when running it.
    - using -h when running the milter will show a short usage help