The setup is this:
One Domain called "adomain" with NT PDC, BDC and member server with Exchange 5.5 SP3 called "mail" , 50 users. A sister company on another site with another NT domain, one PDC, no Exchange server, 15 users.
The domains trust one another and are connected by low bandwidth VPN. The users in "anotherdomain" access their own mailboxes on the Exchange Server in "adomain". All clients in both domains are w2k Pro.
The goal is:
Upgrade all servers in "adomain" to AD w2k, mixed mode, AD domain "adomain.com" . Upgrade Exchange 5.5 to Exchange 2000 retaining name "mail". Allow users in "anotherdomain" to continue to access mailboxes on the (upgraded) Exchange Server in "adomain.com". For the time being the PDC in "anotherdomain" will remain as NT.
Upgrade PDC and then BDC in "adomain" to W2k Server and AD domain "adomain.com". Upgrade NT4 Exchange 5.5 to W2k Exchange 5.5. Install W2k on a new server called "mail" and join workgroup. Backup up mailbox data to .pst files on Exchnage 5.5 server and take it offline. Join new w2k server called "mail" to "adomain.com and install Exchange 2000. Import mailbox data from .pst files.
Will the upgrade path allow users in "anotherdomain" to continue to access mailboxes on the Exchange 2000 server in "adomain.com" and will they still be able to send emails with reply address, say, firstname.lastname@example.org? Any other/likely problems with this upgrade path?
Thanks for your patience!