Well, Exchange 2000/2003 requires AD in order to run anyway, so you would need to upgrade the OS first. Now, here's the kicker. You would need to upgrade to Windows 2000, upgrade Exchange to 2003, then upgrade the OS again. You see, Windows 2000 will support Exchange 5.5, 2000, and 2003, but Windows Server 2003 will not support Exchange 2000 (although there were some people using a workaround with the betas of Exchange 2003 doing OS upgrades, but Exchange 2003 RTM pretty much killed that) and I don't think it cares for Exchange 5.5 either. Also, you will want to use an AD connector to get all of that extra information (metadata) on the mailbox users, such as phone numbers, into your AD. This will probably require the use of a connector, but I have never had a need to upgrade like this before, so don't know how well it works. I have moved 5.5 installs, and upgraded from Exchange 2000 to 2003 on a Windows 2000 box, and then moved all of the mailboxes to a fresh Windows/Exchange 2003 box later on. BTW, if you have the option of installing the new OS and Exchange on a fresh box, and then moving the mailboxes over, that would be best.

Thanks. That's very useful information.

Quote:...BTW, if you have the option of installing the new OS and Exchange on a fresh box, and then moving the mailboxes over, that would be best.

Damn, that's what I was about to suggest: if you don't have too many users, use exmerge to export the mailboxes, recreate your server and reload the mailboxes.
That way you can be sure that there are no "gotchas" hiding somewhere from the upgrade.

Rgds
AndyF

150 mailboxes. I'd like to avoid a fresh reload if possible!