Nymservers and replay attacks?

[Roger Dingledine <arma@mit.edu>]

I've been pondering the reply block issue some more, and I realized I
don't actually know how the current mixmaster/nymserver system works.

The nymserver has an email address and keeps an associated reply block
with it. People send mail to the nym address, and the nymserver forwards
it to the reply block. Is that about it?

Does the remailer system drop replays? How could that work?

Is it that the remailer system is generally type 2 remailers, and the
nymserver uses type 1 (which don't drop replays)?

So is it really the case that nobody has figured out how to do long-lived
reply blocks in the face of servers that drop replays?

--Roger