You must remove all of the connectors, mailbox databases and public folder databases from the affected server before deinstall. Also, you must remove the server from the DAG group after removing the mailbox databases. Don't worry about the physical deletion of the database files warning, it doesn't matter.

EMS: Exchange Management Shell (a command prompt preloaded with all of the Exchange Powershell extensions)

EMC: Exchange Management Console (Exchange GUI tools - MMC snapins)

Problem #1 need to replicate public folder content to other servers, which can be setup easily enough with the EMC tool for public folders. The hard part is that even when you do this, the removal process tells you that there are still replicas out there and you have to remove them before deleting the public folders, the you can deinstall. The trick is to run this script (MoveAllReplicas.ps1) after you are sure the Public folders have had time to replicate to another server. This script is located in ' C:Program FilesMicrosoftExchange ServerV14Scripts' and should be run from the EMS. It takes '-sourceserver [server]' and '-targetserver [server]' flags and runs quickly. However, I've found that it takes awhile to actually complete, and the Public Folder deletion still gives the error and won't work until it's done.

Problem #2 when removing routing groups, especially legacy ones connected to 2003 from 2010. This was also an issue for 2007. From EMS you must run the 'new-routinggroupconnector' cmdlet, which works fine, but then you must remove the old connectors with the 'remove-routinggroupconnector'. The problem is that they want the "-identity", which is described in their "full" help as [administrative grouprouting groupconnector name]. I couldn't get it right and it wouldn't take. There is another option to use the GUID of the connector, but even the "full help" doesn't show how to do this. Online I found that the command 'get-routinggroupconnector | fl' dumps the "real full" set of connectors, including their GUIDs. Then you can jsut run the command 'remove-routinggroupconnector [guid]' and it removes just fine. Then you can uninstall your Exchange Server (for sysprep, decom or whatever), also the command 'get-routinggroupconnector' is used throughout this process.

I've also found the Powershell command 'get-help [cmdlet] -examples' to be very helpful, e.g., 'get-help get-routinggroupconnector -examples'; it's pretty much like a UNIX 'man' command, but with more options.

Read more:

Removing Dead Exchange 2010 Servers | http://www.extropy.com