Microsoft → Re: [Exchange] Exchange keeps looking at a old DC

Sounds like the three "old" DCs weren't properly demoted from the domain and they still have services entries in DNS.

I would make sure the two current DCs hold all 5 FSMO roles then I'd clean up DNS of any entry referring to the "old" DCs.

That should get you started on the way to recovery.

You've nailed it so far. Thank you!

I think I might have this somewhat cleaned up. Thanks again for the help. I'll update you on the progress.