Recent newsgroup posting caught my eye:
I've done cross sites moves today from 5.5 servers to 2003SP1 servers. The documentation says I need the exprofre.exe tool to update the Outlook profiles. But I don't need it, the profile connect automatically to the new server in the other administrative group/site. Why should I use it?
This is a valid question, and one I've been asked a bunch of times while teaching the SP1 Site Consolidation training internally at MS.
The unfortunate truth is that as part of the cross-site mailbox move process, the HomeMDB and HomeMTA attributes are updated on the stub user (see this posting for a mid-level view of what goes on during the move mailbox process). When these attributes are updated, this means that the next time your Outlook client tries to connect to your original 5.5 mailbox server, you will be redirected to your new mailbox server just as though the mailbox was moved within the site. This is totally expected behavior.
So why isn't this ok? Why do you still need to run the Exprofre.exe tool?
Well, remember -- you HAVEN'T just moved the mailbox to another server within the site. In fact, you've move the mailbox data to a completely different 5.5 site, and in doing so you have marked the original site's mailbox directory object as a "stub" object. Further, you have created a totally new mailbox directory object in the target site; a directory object that has a new and distinct "object distinguished name" (legacyExchangeDN in Exchange 200x terms). This is a totally different user as far as Exchange 5.5 and Outlook are concerned.
Outlook is perfectly capable of sorting out an intra-site mailbox move, changing the Outlook profile properties that related to the mailbox server location. It is not, however, capable at present of figuring out that not only has the mailbox data moved, but that the mailbox is no longer associated with the same directory object! After a cross-site mixed-mode mailbox move, the Outlook profile will be updated to point to the new mailbox server location, but the Outlook profile will *NOT* be updated to reflect the new mailbox directory object. Throughout the Outlook profile will be references to the old (now "stub") mailbox directory object in the original 5.5 site. Any time Outlook tries to reference these properties in the Outlook profile, the wrong DN will be returned.
That's the primary thing Exprofre fixes -- the update of the old mailbox directory name to the new mailbox directory name. But it also cleans up a handful of other stuff as well. For more information on the Exprofre utility, what will be broken if it's not run, and what it changes in the Outlook profile please see KB.873214.
Note: There's an even shorter answer to this question if you don't care so much about the technical aspects. Yes, you should absolutely run Exprofre on affected Outlook profiles after cross-site mixed-mode mailbox moves. If you do not either run this utility or recreate the profile as new, the profile will be in a state that has not been tested by Microsoft and results may be unpredictable!