Moved Exchange 2010 to a VM, can't decomission original (physical server)

Moved Exchange 2010 to a VM, can't decomission original (physical server)

We created an exchange VM to replace a physical server, moved the
mailboxes after pointing internal and external DNS to it.
Everything works fine, except when I turn off the original machine, about
half my users lose connection.
A right click on outlook systray for connection status shows Server
'EXCHANGE01 still in the list for those failing... The same list on
failing machines also shows Server exch (the new VM).
Working users only show connection to Server EXCH in the list.
All desktops are identical Dell optiplex's running win7 (same image).
I can't quite figure out what's still pointing them to exchange. Their DNS
is right, a ping to 'mail' shows the right IP for the exch server... so it
must be something in outlook, or some odd config in the server. The fact
that it's roughly half the users is what's throwing me off. All mailboxes
are on the new VM.
I have had SOME users succeed by closing outlook and opening it while ONLY
the exch server was on, but others doggedly stick to waiting for
exchange01.
Stumped