I submit, for your consideration, the following:
The Microsoft IPR license is incompatible with the GPL. This is not
disputed by Microsoft and has been attested to by Eben Moglen. This
means that GPL'ed software will not be able to include Sender-ID code.
Exim is software that is released under the GPL. So how important is Exim?
A quick search reveals that, among many many others, the following ISPs
use Exim:
earthlink.net, inter.net, csolve.net, parasun.net
look.ca, global.net.uk, xmission.net
demon.net, shore.net, pol.co.uk
t-online.net, freenet.de, uk2.net
direct.ca, kundenserver.de, powercom.net
psi.net, atlantech.net , net4india.com
uksolutions.net, zen.co.uk, liquenox.net
blueyonder.net, rcn.net, mec.net
Also, among many others, the following educational facilities use Exim:
Youngstown State University, Imperial College London, University of
Central Florida
Cambridge University, Loughborough University, MIT
Cranfield University, University of Bath, Harvard University
University of Manchester, Oxford University, University of Texas
University of Utah, University of East Anglia, University of Hawai‘i
University College London, University of Essex, University of Houston
University of Sheffield, Lander University, California State University,
University of California, University of Northern Iowa, University of Toronto
University of Oregon, University of Illinois, Florida State University
As Sender-ID relies on rapid adoption, and there are so many major ISPs
and Universities that will not be able to adopt it without changing
their MTA, I just don't see how anyone could endorse Sender-ID. The GPL
issue is going to hamstring widespread adoption.
Kevin