Moving users to new Exchange organisation in new domain

[ClowneUser]

Hi,
We have a sister company who is in the same AD domain as our company (w2K domain called CompanyA), but on a different physical subnet connected by a WAN.
We want to migrate their users and applications to a new domain, CompanyB, and upgrade them to AD W2K3.
I've asked questions about this in a separate thread, but my question here is about the Exchange migration.
Currently all Company A and Company B's users are in one Exchange organisation called CompanyA.
We need to install a new server running W2K3 server and Exchange 2003 at CompanyB's site, and create a new Exchange organisation called CompanyB. All the users of company B will then be migrated over to the new server/exchange organisation.

Does anyone have any advice for doing this properly, including any utilities we could use for migrating the mail already in users' mailboxes, etc. and any pitfalls we should look out for?
Thanks in advance for your help.....

 

[Zelandakh]

Unless there are loads of users, suggest using exmerge. Export the mailboxes to a bunch of PST files, stick them on a USB drive, cart them to the new premises, use exmerge to upload them to the new exchange server once you have created new AD accounts with empty mailboxes of the same names.