On Jan 21, 2007, at 9:11 AM, Johan A. van Zanten wrote:
>  How about going to listmember-only posting but adding a whitelist of
>  other, non-listmember senders?  It seems like with Postfix, it  
> could be a
>  "From" line whitelist, or maybe a mail relay white list.

In principle, that's what I've been advocating since 2001.  The  
actual implementation details are unimportant.  There are N ways to  
implement it and N-1 people willing to debate the merits of each  
approach.