The homeMDB attribute is reset after you move mailboxes from Exchange Server 5.5 to Exchange 2000 or to Exchange 2003

After you move a mailbox from Microsoft Exchange Server 5.5 to Microsoft Exchange 2000 Server or to Microsoft Exchange Server 2003, the homeMDB attribute may be reset to the Exchange Server 5.5 computer. This issue can occur if a modification is made to the Active Directory object before replication within the site updates the Exchange Server 5.5 computer that is the target of the Recipient Connection Agreement.

Exchange Server 5.5 directory replication always replicates the entire object with all of the object's attributes. The same limitation applies to Active Directory Connector (ADC) replication. However, replication between Microsoft Windows 2000 domain controllers occurs at the attribute level. Because of the object-level replication between Exchange Server 5.5 computers, a replication conflict can be generated if two attributes of the same object are modified on two different servers in the site. In a replication conflict, usually the most recent change is replicated, and the earlier change is discarded.

During a Move Mailbox procedure between Exchange Server 5.5 computers, you must make sure that the mailboxes are not modified on a third server because that modification can override the homeMDB attribute change and rehome the mailbox. This issue also applies to a move from an Exchange Server 5.5 computer to an Exchange 2000 computer or an Exchange 2003 computer.

For example (for Exchange Server 5.5), assume that servers A, B, and C belong to the same site. User 1's mailbox has version 5 on all three servers. If you move user 1 from server A to server B, first the data is copied, and then later the homeMDB attribute is updated from A to B. The object version is incremented to 6 on server A and B. If user 1's mailbox is modified on the third server (server C) at the same time, before this server is updated with the new homeMDB attribute information, a conflict is generated. For example, if the office attribute is updated on server C, the version of this object is again incremented from 5 to 6, but the change time might be later compared to the change time on servers A and B. In this replication conflict, this change is replicated; the changed office information is kept, but the updated homeMDB attribute is discarded.

To work around this issue, use one of the following methods, as applicable:

• Prevent any other modifications to the Windows 2000 user objects until all of the Exchange Server 5.5 computers in the site are updated with the new homeMDB attribute information. You can use the Active Directory Replication Monitor tool (Replmon.exe) to track changes on Windows 2000 objects; for additional information about using Replmon.exe, see the "More Information" section of this article.
• During the move, set replication to Never for the Recipient Connection Agreement, and make sure that the Exchange Server 5.5 site is up to date before you re-enable replication.
• In a small scenario, you can point the Recipient Connection Agreement to the Exchange Server 5.5 computer to make sure that the Recipient Connection Agreement always points to a server that already has an up-to-date homeMDB attribute.

During a Move Mailbox procedure from Exchange Server 5.5 to Exchange 2000 or to Exchange 2003, after the data is copied to the Exchange 2000 computer or the Exchange 2003 computer, the Move Mailbox Wizard updates the homeMDB attribute on both the Exchange Server 5.5 computer and the Windows 2000 domain controller to which the Users and Computers snap-in is connected.

Using Replmon.exe to track the change on the Windows 2000 objects

You can use the Active Directory Replication Monitor tool (Replmon.exe) from the Windows 2000 Support Tools to help track replication. This tool can display the update sequence numbers (USNs) and version for all of the attributes of an object. To view the USNs (or metadata):

1. Start Replmon.exe.
2. On the Edit menu, click Add monitored server.
3. Right-click the server.
4. Click Show Attribute Meta-data for Active Directory Object.
5. Click the USN column to sort by USN number.

Immediately after the move, the following attributes display the highest USN and latest change time:

• homeMTA
• homeMDB
• msExchHomeServerName

The other domain controllers and the Exchange Server 5.5 directories, including the Site Replication Service (SRS) directory, still have the older objects and old homeMDB attribute values. If no other change occurs, the version number of the older objects and old homeMDB attribute values is still lower, and replication within a site updates the Exchange Server 5.5 computers and domain controller replication updates the Windows 2000 Server-based computers.

Important information about ADC and homeMDB attribute replication

The ADC only replicates homeMDB attribute changes if the mailbox is moved between Exchange Server 5.5 computers, between Exchange 2000 computers, or between Exchange 2003 computers. If one of the target servers of the Connection Agreement shows the mailbox on Exchange 2000 or Exchange 2003, and the other has the homeMDB attribute set to Exchange Server 5.5, the homeMDB attribute does not replicate over this connection. The Move Mailbox Wizard is responsible for updating both the source server and the target server with the new homeMDB attribute.

Modifying the Windows 2000 user object resets homeMDB attribute

As soon as any other change is made to the Windows 2000 user object, the Recipient Connection Agreement replicates the change. If the Exchange Server 5.5 target server of the Recipient Connection Agreement still shows the old homeMDB attribute, ADC replication might cause issues. The object is updated and the version number is increased, but the homeMDB attribute is not updated on the Exchange Server 5.5 computer. In the replication conflict in the Exchange Server 5.5 site, this object is replicated and resets the homeMDB attribute on the other servers.

Two mailboxes are generated

If you send mail to or connect to the Exchange Server 5.5 mailbox with Microsoft Outlook, an instance of the mailbox is created in the store of the Exchange Server 5.5 computer. This mailbox will be visible in the mailbox resources for the server. From that point on, the user has two complete mailboxes: the Exchange 2000 or Exchange 2003 mailbox with the old content, and another mailbox getting new mail on Exchange Server 5.5. To resolve this issue:

1. Save the contents of the new mailbox to a personal folder (.pst) file.
2. Delete the Exchange Server 5.5 recipient object to remove the Exchange Server 5.5 mailbox.
3. Replicate the deletion to Windows 2000.
4. Reconnect the Windows 2000 user to the Exchange 2000 or Exchange 2003 mailbox.
5. Copy the .pst file data to the Exchange 2000 or Exchange 2003 mailbox.