Multihomed / Failover IMAP Config?

[jon at ics.com]

I've been using my cable modem for years to host my home email server
(smtp.tangentrix.com)  but with everyone blocking mail from dynamic IP's
I've decided to move my server to a real hosting facility.  The only
problem is that if my server flakes out I'm going to run into problems. 
And it could be days before I'm able to get down there and fix it so I'd
like to keep my current server (on my cable modem) as a backup.

I already have my DNS setup so that the server in the co-lo facility is a
secondary DNS entry (for testing).  I'm using courier-imap and postfix on
both boxes.

Is there anyway to setup courier-imap in a master/slave configuration?


Thanks,
Jon

P.S. I'm not about switching to a different IMAP server if I need to.