[exim] Sharing autoreply once data without using NFS

Hi all,

I'm doing some work on using Exim for a group of mailrouters. Each box runs
independent and uses LDAP for the information they look up. Vacation
messages and autoreply messages are being setup using the autoreply
transport.

Right now, I have 4 boxes (2 in use) and will probably grow to 6 when we
start. These servers will be extremely busy when the project is done, so
I'm not too receptive to creating dependencies on things like NFS. I'm now
stuck with how to prevent duplicate vacation messages from going out from
each individual mail server as they see the source address for the first
time.

I'm leaning towards doing something like nominating one server to handle all
vacation messages, with another server doing "backup" if the first is down.
It is relatively easy to keep a set of files in sync over 2 servers then n
servers.

I'm wondering if there is some other approach that I haven't considered yet
that might work better. Or for that matter if I just haven't searched the
FAQ's fully to find the answer. Any comments or advice would be
appreciated.

Thanks.

Erik.