I recently had to force demote one of our old domain controllers. I could not demote it gracefully or forcefully, I had to just shut it down and delete the server from ADUC. I've gone through and cleaned up DNS and metadata and the other AD utilities and things seem to be pretty clean. However, that server had an old Exchange 2003 on it. All of the mailboxes and folders in this Exchange 2003 were moved to our Exchange 2010 a few years ago and it has been functioning properly since. Exchange has been functioning properly since I turned off the old server as well, so our new Exchange server doesn't seem to have any reliance on the old one. However, the Exchange 2003 uninstall didn't go smooth either and ESM and other functions remained on the server, albeit they were dead and turned off.
My question is this. I can't create address lists because it tells me I have legacy servers in the mix. I found articles that tell me to use ADSIedit to delete the old server reference in Configuration - Services - Microsoft Exchange - domain - administrative groups - first administrative group - servers. In here is a reference to my old server. Can I delete that? Also, since Exchange 2010 uses "Exchange Administrative Group" and "First Administrative Group" is no longer used can I delete that entire tree? Further, there is references to both of my old DC's in Configuration - Services - Microsoft Exchange - domain - Connections. Can I safely delete these? They mention servers that are both Server 2003 DC's and offline for good.
Finally, is there any other known areas for me to delete old Exchange or Server 2003 references when manually cleaning up old Exchange installs from AD? I'd like to get this all cleaned up for preparation to move to Exchange 2013 at some point.