Opening a mailbox in a different Exchange 2003 Org / Trusted Domain

Need a temporary fix if possible.

I have two 2003 domains, trusted both ways.  Each has their own Exchange organization.

A user in Domain1 would like to be able to open his mailbox in Domain2 using Outlook until we can get everything migrated properly.  I know I can assign the right mailbox rights but how do I convince Outlook to look outside its own AD domain when setting up an Exchange profile?

Understand this is just a patch.  Any ideas appreciated!
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What I understood from your descripton that You have messaging System in A.D. domain and user from A.D. domain wants to access this mailbox. If this is correct, please follow below steps:

- Create two way trust relation between and
- Create a mailbox in for user from (Lets user from is and user from is
- Disable Go to properties > Mailbox Rights > Select from and give him Full Mailbox Access + Associated External Account.
- On DNS server in, configure forwarder to forward all queries for to DNS Server in
- While configure Outlook profile in, user always FQDN name for mailbox server.

Please let me know if you need any clearification.

as far as i know outlook can only have one exchange mailbox configured at a time. are you trying to use the open other users folder feature within outlook?

The process that you are trying to do is Creating Linked mailbox accounts. This involves several steps.

lets Say Forest A has Exchange Mailbox accounts.
Forest B has users account who wan to access Mailbox accounts in Forest A

Requirement Two way Trust RelationShip between forests
Create disabled user accounts in Forest A with Mailbox A
Grant mailbox right on AssociatedExternalAccount Account attribute to ForestB user.

Please check the following article
Granting Access to External Accounts,EXCHG.65%29.aspx

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FiginAuthor Commented:
Does the user account in Domain1 (the one he wants access to using his Domain2 account) *have* to be disabled?

Currently, there's a bit of a hodge-podge of access where he actually uses both accounts for different things (strange but that's how it is set up).  

We ultimately want all the Domain2 user accounts to be migrated over to Domain1 but unfortunately, that's several months off before I can do it.
could you just forward the user's domain2 email to the domain1 address?
users in should be disabled.
Mike ThomasConsultantCommented:
Seriously I would just use Outllok Web on the other domain this way he can have both mailboxes opened on the one PC, or access both remotly. If it just a short term thing that should be fine
FiginAuthor Commented:
All good thoughts and comments!

The user refuses to use OWA and doesn't want things forwarded.  He wants to use the mailbox in Outlook native.

I guess I'm just wondering what the rationale is for having the resource mailbox account disabled?  He would not be using that account to access mail (he wants to use only his current trusted domain account) but wants to use the same mailbox account for other access.  We're having a time working through all the domain migration details so we can't just do it in one fell swoop.  But yes, this would be a temporary thing, just trying to confirm whether not disabling the account will break anything else on the mailbox account.

Thanks again.
Disabling the account in resource forest is a requirement the way Linked mailbox works. mailbox will still be accessible because user in account forest will have full access and external associate rights on it.

It shudn't be breaking anything unless he uses resources forest account for some other purpose like file access, login, etc etc
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