Removing the Last Exchange 2003 Server...
Microsoft has lots of guidance about removing the last Exchange 2003 server from an administrative group (see KB 822931) and I definitely recommend you give that a read. They also have a technet article about removing the last Exchange 2003 server from your organization (after you've upgraded to Exchange 2007, of course). You should give that a read too.
But if you do these things lots of times (and if you are a consultant, you probably do - or if you play in your Exchange lab a lot, you probably do too); you just need a quick list of reminders. Here is the list I take onsite with me, when I'm removing an Exchange 2003 server:
Verify that all mailbox moves are complete (either within the console or "get-mailbox -server <servername>").
Verify that all public folder moves are complete ("get-publicfolderstatistics -server <servername>"). Note: if they aren't this can be tough. Check the scripts in $ExScripts like MoveAllReplicas and RemoveReplicaFromPFRecursive.
If you do NOT have an Edge server, verify that the Default receive connector allows Anonymous connections.
If you DO have an Edge server, verify that Edge synchronization has occurred and is operational ("test-edgesynchronization").
Move all Offline Address Book generation servers to servers that will continue to exist
Move the "Default Public Store" on all Exchange 2003 Mailbox Stores to point to a Exchange 2007 PF
Delete the Public Folder databases from the Exchange 2003 server (note: this is not a required step, but if you can't do this, then de-install of Exchange will fail - so this is a good place to go ahead and figure that out).
Delete both sides of Interop RGCs (and verify that they are the only RGCs still present: "get-routinggroupconnector")
Delete SMTP connectors from ESM on the Exchange 2003 server (you can do this from the EMC on Exchange 2007 later, but you'll get a version warning)
Evaluate Recipient Policies and delete all unused RPs from ESM on the Exchange 2003 server
Verify status of all recipient policies (ensure that Mailbox Manager boxes are unchecked)
Note: you may want to record Mailbox Manager settings to recreate MRM policies on Exchange 2007 to replace the MM policies
Relocate the PF heirarchy (in Exchange 2003 ESM, right-click the Exchange 2007 Administrative Group, select Next -> PF Container, drag PF object from the Exchange 2003 Administrative Group to the Exchange 2007 Administrative Group)
Delete the Domain Recipient Update Service(s) from ESM on Exchange 2003
Point the Enterprise Recipient Update Server to an Exchange 2007 mailbox server (or delete the RUS from Active Directory using adsiedit or LDP)
Now, this is one of those postings where I have to say "this works for me". I bet it'll work for you too - but I can't guarantee it!
Until next time...
If there are things you would like to see written about, please let me know!