Exchange 5.5 to qmail & Courier IMAP migration.

I have an Exchange 5.5 mail server currently receiving mail for my
company. I have set up Qmail and Courier IMAP on another machine with
all required email accounts established. What I would like to do is
have email sent to both machines as I move one user at a time from
Exchange to the Qmail server.

My MX record is setup for mail.mailwatch.com who scans all of my email
then sends it on to the ip of my choosing. Thus, just switching over
would be trivial, but would cause a disaster in productivity while I
ensure my users are properly configured. It would also force me to be
"live" without having the opportunity to finish testing completely. I
am not prepared for such an undertaking.

So my question is:
How do I copy incoming mail to my Qmail server and enable a user to
check their mail on both until the Exchange server can be completely
phased out?

I did this exact migration (EXIM instead of qmail) - however, I never
found a way to split the messages.  You could set up a .forward or
equivalent in qmail and redirect it to a sub domain that the exchange
server picks up (make sure that it keeps a copy locally), traslates
down to the base and stores. huh, maybe that is the solution.

What I eventually did was made a script that connected to the imap
server of the exchange and just blew through all the accounts updating
the new system.

best of luck

I have looked into that with qmail, setting up aliases from Qmail to
my exchange server. But I need to do it in the opposite direction -
from exchange to qmail. I probably wouldn't mind the opposite
direction if I could test the server in operation, but since I can
only test if it is installed correctly, I don't feel confident in
switching over to the Qmail server and forwarding on the mail.

well in 5.5 it is easy, you can set up forwards for each account and
then send it to a sub domain that qmail answers for