When you upgrade the forest to a Microsoft Windows Server 2003 native forest functional level, the Recipient Update Service may overwrite the value of the homeMDB attribute for new Microsoft Exchange Server 2003 users. This behavior may cause the mailboxes for the new Exchange Server 2003 users to be rehomed on the first mailbox store in the first storage group.
In Windows Server 2003, the homeMDB attribute is marked for Linked Value Replication (LVR). When you set the forest to a native forest functional level, the forest changes the way objects replicate with regard to LVR. When an object that has LVR attributes replicates to other domain controllers, the object replicates the non-linked attributes first. Then, the object replicates the LVR attributes that follow in a separate replication packet.
This behavior causes the Recipient Update Service to see an Active Directory account without the homeMDB attribute present. This behavior occurs even when this attribute exists on the original domain controller. Therefore, the Recipient Update Service overwrites the value of the homeMDB attribute if either of the following attributes exist:
The msExchHomeServerName attribute
The homeMTA attribute
To resolve this problem, you must modify the purportedSearch attribute before you upgrade to a Windows Server 2003 native forest functional level. To do this, follow these steps:
Start Active Directory Service Interfaces (ADSI) Edit.
Double-click the Configuration container, expand CN=Services, expand CN=Microsoft Exchange, and then expand CN=<ExchangeOrganizationName>.
Click CN=System Policies.
In the right pane, right-click CN=Mailbox Enable User, and then click Properties.
Scroll down to select the purportedSearch attribute, and then click Edit.
Clear the attribute, and then use the following filter to configure the attribute: