Thanks for your discussion.
One correction, the muttering about "unsupported methods" is actually
from:
http://www.postfix.org/addon.html#content
which is perhaps slightly more creditable than geocities.
Googling around a bit I got this thread with thoughts from one of
the main developers (Wietse Venema)
http://archives.neohapsis.com/archives/postfix/2003-08/0511.html
http://archives.neohapsis.com/archives/postfix/2003-08/0513.html
http://archives.neohapsis.com/archives/postfix/2003-08/0514.html
http://archives.neohapsis.com/archives/postfix/2003-08/0515.html
http://archives.neohapsis.com/archives/postfix/2003-08/0522.html
http://archives.neohapsis.com/archives/postfix/2003-08/0595.html
[the threading at the archive was not good so I included links to whole
thread]
I might feel differently if our server was heavily burdened, but the
prospect of breaking things with an upgrade to postfix not worth the
speed.