Through out migrations and site consolidations it is common for administrators to create multiple accounts for users. Certain situations can cause problem for clients when they are trying to download the OAB. Below is the break down on the process:

• Each Offline Address List is linked to an Address list
• Each mailbox information store has an Offline Address List associated with it. You can have four (4) different mailbox stores with the same Offline Address List associated or four (4) different Offline Address List's and one different one for each information store.
• When a client logs in to the information store the information store will get the DN of the OAB from the mailbox stores objects (msExchUseOAB attribute) and convert this to an EntryID.
• This EntryID is given back to the client and links to to the OAB system folder that the client is supposed to download.

Now if an administrator incorrectly configures users account problems downloading the OAB can start to happen. These problematic users are users that have two user accounts in the same AD forest

• A disabled mailbox-enabled user account in the domain where Exchange was installed, and their enabled account in a different domain.
• This enabled account was set as the Associated External Account on the disabled account.

Under this condition if the user attempts to download the OAB a sync error will occur:

Task 'Microsoft Exchange Server' reported error (0x8004010F) : 'The operation failed. An object could not be found.'

How to Fix
Disconnect the mailbox from the disabled account and connected it to the enabled account.

Dave