Before the question, some background:
I've been running Exchange 2010 as CAS, Hub, Mbx on a server (Server4) running 2008R2 for some while. This machine is also DC and running DNS plus some other roles (think SBS2008). I added another machine (Server5) also DC in the same domain/forest, DNS, GC and also running Exchange 2010 on same OS.
I moved the mailboxes without problem and Get-Mailbox shows them correctly on Server5. Users can use OWA fine but when I go to point Outlook (2003 or 2007) at the new server, it insists on changing the entry back to Server4 as soon as the "Check name" is clicked. However, Outlook still works until I power down Server4 and then I get the message that the Exchange Server can't be contacted - quite reasonably!
I have transferred all FSMOs to Server5 and done everything to ensure that Server5 can stand on its own but I don't yet want to remove the Mailbox and other roles from Server4 - just power it down for periods. In case it's relevant, I have set up the mailbox database on Server5 to be replicated to Server4 using a DAG.
Now we can get to the question: Why does Outlook insist on retaining Server4 as the users' exchange server? Where does it get this from and why can't I manually change Outlook to point at Server5? Remember get-mailbox shows the correct Server5 and I had assumed that the server's determination would be from somewher in AD linked to that. Is there a setting somewhere for preferring one Hub or Mailbox server over another?
Any suggestions welcome. Thanks.