[Mailman-Users] Spam avoidance, revisited: best practices?

[Matt England]

This is the best email I have yet to find describing how mail.python.org 
proactive kills spam:

http://mail.python.org/pipermail/python-list/2006-March/332443.html

I'm also considering adding these capabilities (which may or may not be 
implicit in the above description) to combat spam:

* Don't allow email from non-subscribers
* Moderate email from new subscribers some period of time (probably a day 
to a week)

Does mail.python.org do either or these things and/or is this generally a 
good practice?

Any other suggestions?

-Matt