I have two Exchange 2010 servers in two locations (and one Exchange 2007 at one of the places but this one is not really in use nor causing any problems) - one server per site (say site A and site B). Sites are on different network ranges and there is a routed tunnel set up between sites. Users' mailboxes are spread out between those two servers so users access to their mail locally rather than through slow WAN link. There is a DC and DNS server per site, and DNS resolves names correctly.
The problem is with Outlook account configuration - no matter what I do, when the site B Exchange server name is entered in Outlook, Outlook resolves the name to the Exchange server from site A. I tried using the server name (Company-EX02), FQDN (Company-EX02.domain.local) and the IP address but nothing makes any difference (this happens from either site, not just site B).
I might be wrong but as the connection speed seems to be worse now (I did not do proper tests before the change so can't really say for sure) I have a feeling the traffic still goes through slow WAN link but actually multiple times - first the user's mail client speaks to EX01, then EX01 speaks to EX02, then data is moved back to EX01 and finally to user at site B.