I have the same situation, and I think I have a pretty good solution.
I have set up my laptop with an open-source IMAP mail server. Both
desktop and laptop refer to this mail server, instead of my "real"
mail server. I set up my router to give the laptop a static DHCP IP
(because the mail server is easiest to set up with a fixed IP
address). I then set up Outlook Express 6 with IMAP accounts that
read off the IMAP server.
The IMAP server I use is Hamster Classic, version 2.0.0.1, which can
be found at
http://www.tglsoft.de/misc/hamster_en.htm. It's designed
and compiled for Windows (I use it on Windows XP, though I think it
works for 98 and up). The only trouble I have with it is that it was
originally designed in German, and ported over to English. I had
tried out an earlier version (which they called stable), and found
that it did not have either IMAP or a manual in clear English. The
newer version is much better. Additionally, there is a lot of good
help on their newsgroup hamster.en.config.
One thing, I forgot that was a little tricky... I am pulling my mail
off of a POP3 server. You have to have a script to tell it to check
the POP3 server on startup. Fortunately, they have provided a sample
script in the manual.
Also, you need another tool to run Hamster as a service. There's good
instructions for this on
http://www.elbiah.de/hamster/hamsvc/index.htm
(it has a download link too. It's provided for a spin-off version
called Hamster Playground, but it's compatible with Hamster Classic.
It's taking a little getting used to, as IMAP and POP3 act a little
different under Outlook Express. So far, however I'm pretty
satisfied.
Hope that helps,
Michael English