We have a local wireless network (>3000 mailboxes spread over 20 domains).
However, as we're situated in a rural area, we do not have access yet to >4Mbps ADSLs.

I've been running 3 Zimbra servers for some years now, each on a dedicated DSL line and apart from occasional sending backlogs, it's been working great.
The advantage of the server being local, is that sending/receiving from the user perspective is very fast and mail can trickle in/out at it's leisure.

Our problem however is that we also sell DSL accounts and we have users that travel, so they need to receive mail (POP/IMAP/ZWC/ZD)from outside the network, i.o.w. over the same oversaturated DSL connection, which varies from slower-that-dial-up to non-exsistent, which is to be expected.

We can have a remote server directly on Internet backbone, which would be great for remote users, but slower for local users.
So my Question is:
Would it be possible to have a 'main' remote (on the Internet)server that receive/send, with e.g. 30 domains, then have 3 more local servers, that trickle off the main server. I.o.w. the domain would be duplicated so that users accessing the local server's ZWC would see the same data as when they access the remote server's ZWC.
I hope it makes sense.