Remote IMAP Mirror - Suggestions?

[Darren Joy]

Well, after an immense struggle, I have persuaded Cyrus to actually work.
I've never experienced such huge problems with any open source software,
this is by far the worst, by orders of magnitude. My main problem I think
was expected the test programs to work, i.e. imtest and pop3test etc.
They're horribly broken, and reported that Cyrus wasn't working, when in
actual fact....it was. Extremely annoying, and a lot of time wasted on
this, I hope the distribution gets sorted out properly very soon, and some
accurate documentation would be nice as well.

Anyway, rant over, now it's working, on to stage two.

I have two cyrus IMAP servers, they're not currently, but assume they will
be running the same versions, 2.1.12 of sasl and cyrus imapd.

One of them is the actual mail relay and MX host, and is located around
8000 miles away on the edge of a continental rift, and the other is local
and behind NAT. The MTA is sendmail, though it's not tied into cyrus/sasl
at the moment. Also used is procmail.

What I would like to do is run a live mirror of the offsite mail server on
the local machine. I could of course just backup the imap mailspool, and
store it on the local machine in case of disaster, but I'd like to also
have it *useable* in case the link to the remote mailserver goes down for
any reason ( like California falling into the sea! ).

I'm not expecting two way mirroring (though of course that would be nice),
but even the ability to bounce a copy of every mail to the local mail
server would be a significant bonus to me to.

I'm looking for suggestions for how to go about this, which software to
use, if I can do it with my current software or if there's some wizzy
package out there which is just brilliant at this sort of thing.

Anyone done anything similar to this?

-- 
Darren Joy