Providing an initial OST file for an Outlook cached Exchange mode deployment

Posted on 2009-04-13
Last Modified: 2012-08-13
I need to use the procedure at in connection with a change of domain membership on some client computers.
The user of each computer has an account in the old domain and an account in the new domain. I intend to use the procedure documented in the above page to provide an initial OST file for Outlook while running under the new domain. Some users are running Outlook 2003 and some are running Outlook 2007.
I would like to know whether anybody has tried this and whether there are any caveats that the above page does not highlight. I would like feedback on both Outlook 2007 and Outlook 2003 to award points.
Question by:lightseekertoo
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Expert Comment

ID: 24148251
You're better off logging in on the old domain, exporting to PST, then opening the account on the new domain and importing the PST. Extra steps from what the article describes, but it's a bit simpler and will definitely work. We do this all the time.

Expert Comment

ID: 24148310
I agree. PSTs would make things much easier. How many users? I have found that it is usually better to not mess with the OST files.

Are the clients running in cached exchange mode?

Author Comment

ID: 24159900
Either I was not clear or I am misunderstanding your recommendations. Bear with me and let me re-phrase this.

First, some more background info:
The mailboxes exist and are being accessed using RPC over TCP/IP from within a Windows profile that belongs to domain A. The Outlook profiles are all set up to use cached Exchange mode.

Second, a clarification of what I intend to do:
Taking a particular person PX using computer CX, I shall be disjoining computer CX from domain A, joining CX to domain B and creating a user account on domain B for person PX to use. Domain B holds the Exchange server that holds PX's mailbox.

Why I can't understand your recommendation to use PST files:
1. My worst-case scenario would be to re-create the Outlook profile in domain B's  user account for PX using cached Exchange mode and thus re-create the OST file. This would involve the download of a cache of PX's mailbox in the OST file.
2. My best-case  scenario would be to move the OST file to the newly-created Windows profile (which does not involve material data transfer) and configure the  new Outlook profile with the location of this pre-existing OST file.
3. Exporting to PSTs does not seem to be relevant as the Exchange mailbox will not be affected by the disjoining of computer CX from domain A and its subsequent re-joining to domain B.

The Microsoft article quoted seems to be the solution for me in order to avoid my worst-case scenario and what I would like is a comment regarding hidden caveats, if any.

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LVL 15

Expert Comment

ID: 24160290
Those are for the same user in the same domain. The OST file is linked to a user in a domain and cannot be ported to another domain. That's why PST is your best bet. You lose nothing and can port it across the domains.

As soon as you disjoin from domain A, you lose access to the OST without 3rd-party software (which I can recommend). Export to PST before doing this and all will be well.

Author Comment

ID: 24160412
"Those are for the same user in the same domain."

I agree with that statement. The Outlook profile that person PX presently has in domain A is using the account that person PX will be using in domain B to authenticate. The OST file won't be re-linked to a different user. There is no change of user as far as the OST file is concerned.
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Expert Comment

ID: 24160492
They are completely different domains, correct? Are they in the same forest? Just because the username is the same does not entail the same user GUID, which will be different for different domains if they are in different forests.

Author Comment

ID: 24160672
Yes, they are completely different domains in completely different forests.

The username in domain A is not even the same as the username in domain B. Let me call PX's username in domain A with the name UPXA and PX's username in domain B with the name UPXB. I do understand that UPXA and UPXB are different, unrelated objects having different GUIDs.

I don't think that this independence between UPXA and UPXB is relevant because while person PX is operating using UPXA's profile on computer CX, Outlook is connecting to the Exchange server in domain B using UPXB in domain B to authenticate. When the profile is set up for UPXB on CX, Outlook will be using the same user account.

I may be wrong regarding whether this is relevant or not but in any case I will test this over the coming days using a test computer and a pair of test accounts.

I seem

Author Comment

ID: 24160704
The last "I seem" in my last post should have been omitted.

Accepted Solution

lightseekertoo earned 0 total points
ID: 24196222
I have successfully implemented the procedure described at I have used OST files as large as 5GB while following this procedure and have saved a great deal of time in resynchronisation.

I would like to close this question and ask for a refund. I am asking for a refund because the answers provided did not take my scenario properly into account and if applied would have resulted, at best, in a lot of lost time.

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