How to publish Outlook Anywhere 2007 using NTLM security with TMG 2010

Whilst you set-up Outlook Anywhere from the Exchange console, it's actually using the RPC proxy feature, which is separate to Exchange. Exchange doesn't actually care where the RPC connection comes from, whether its local or over http, as they all look the same when they get to Exchange, the RPC proxy and IIS handle the incoming traffic and forward it to Exchange.

To get some statistics on how many RPC users you have your going to have to look at the IIS logs. There is a good article here on using Log parser to get these kind of statistics.

For example, getting the RPC statistics would look like this:

logparser "SELECT cs-username, Count(*) AS RPCProxyHits from c:\windows\system32
\logfiles\w3svc1\ex*.log WHERE cs-uri-stem LIKE '%rpcproxy.dll%' AND cs-username IS NOT 
NULL GROUP BY cs-username ORDER BY RpcProxyHits Desc" -rtp:-1

If you really don't have any Exchange server in your domain, your best bet would be to fire up your trusty ADSIEdit and remove the Exchange Organization object. It should be in Configuration\Services\Microsoft Exchange\OrganizationName. If you remove "Microsoft Exchange" under "Services", all Exchange-related informations should go away.

You should also remove the computer object for the old Exchange 2007 server(s).

If even after this cleanup the installer keeps complaining, try manually running setup /PrepareSchema; this should take care of schema version mismatches, if there is any.

Oh, and it would also be useful to check if your domain controllers are properly replicating; maybe they aren't, and one or more of them still have Exchange-related objects lingering around even if you removed them.