Can murder be used for IMAP server migration?

[Gary Mills]

My current e-mail server has both SMTP and IMAP running on the same
machine.  I'm building a new IMAP server on a different machine that
will ultimately have ten times the capacity.  I'm looking for a way to
migrate mailboxes from the old server to the new one without shutting
down the whole service for an extended period of time.

Can I use the old server as both a front end and one of the back ends
for a murder configuration, with the new server as the second back end?
Will that allow me to migrate mailboxes at my convenience?  How do I
prevent a port conflict between the IMAP server and the proxy on the
old server?

Do I have to run the same Cyrus version on both machines?  Currently,
the old server runs cyrus-imapd-2.1.14 and the new one runs
cyrus-imapd-2.3.6.

Is there anything that won't work in this configuration?

-- 
-Gary Mills-    -Unix Support-    -U of M Academic Computing and Networking-