What is beginning to happen around the net -- with 'responsible' ISPs --
is the enforcement of Forward-confirmed reverse DNS (FCrDNS)

	http://en.wikipedia.org/wiki/Forward-confirmed_reverse_DNS
 -and-

Sender Policy Framework (SPF)

	http://en.wikipedia.org/wiki/Sender_Policy_Framework

In a nutshell, lists email distribution is affected because the emails
are re-sent by the list server as From: The_Originator@....
Which is true -- it did originate "From:" me, or "From:" you.
But, it appears to be a forgery to incoming mailservers that do this
checking, because those emails CANNOT be "From:" that user from THAT MTA.

For example, this email - From: Jonesy <trinity@...>  cannot
be sent from the mail servers at vali.starlink.edu  ---  at least not
with FCrDNS checking.

FCrDNS cuts down on A LOT of spam.  My SysAdmin says 90% of incoming
email is pure crap spam -- with forged "From:"s out of cracked botnet
machines.  FCrDNS cuts down on ALMOST ALL of that.
Think of the savings...

But, I've had to remove my domain from that checking by my ISP because
I am on so many lists, email reflectors, what-ever-you-call-them.
Eventually lists will have to evolve to some different scheme.

Too much information?
Jonesy