I noted the reference to Isode's PP (we do still call it PP, but for
marketing purposes it goes under the title "Internet/X.400 Message Switch".)
I hope you won't mind if I continue to refer to it as PP. I don't call PMDF by
its marketing name either, for that matter.
You are correct that PP does not implement SMTP pipelining and that it
is "pipeline clean". I don't think we would claim pipelining unless
we made the servers take advantage of it (not a big deal to code, but
I can't see much benefit, although you would need it for this sort of
extension).
Um, this demonstrates a misunderstanding of the benefits of pipelining. A
server that claims pipelining but _clients_ are the ones that take advantage of
it. As such, it is beneficial to the community for a pipeline-clean server to
claim pipelining even if the client in the same software package doesn't take
advantage of it (yet).
And if you don't see the advantage, well, I would suggest that you do some
additional timing of SMTP behavior on high latency links. Pipelining often
makes a significant difference.
You are incorrect in your belief that PP does not implement ESMTP. We
have supported ESMTP for some long while and continue to add ESMTP
extensions. However, the current relase (not the release which is
about to ship) can be built with ESMTP turned off, so you will see
deployed systems which appear not to have ESMTP.
Then you might want to consider enabling it on the version of PP that serves
isode.com. Both it and the half-dozen other PP servers I tested did not offer
ESMTP support.
Ned