The correct address for subscriptions is
ietf-ack(_at_)ics(_dot_)uci(_dot_)edu(_dot_)
There has also was some private discussion of this issue in connection
with the ESMTP development, to the effect that the ACK request
information has to per carried in the ESMTP envelope on a per
recipient basis, in the ESMTP envelope, and not in the RFC822
envelope.
The ESMTP extensions were designed to allow for the ACK information to
be carried with each RCPT-TO.
This strongly implies that it cannot be carried via non-ESMTP
conformant SMTP MTA relays.
So, to deal with all this, we are going to have to do some interesting
thinking about how to enable ESMTP upgrading without forcing an flash
cutover of all SMTP relay servers in the extended Internet EMail
network.
More later as this develops...\Stef