1 - Using Active Directory Users and Computers browse to the users AD object.
2 - Right click and select Properties
3 - Click the Attribute Editor tab (if the tab is not available, select View | Advanced Features).
4 - Verify the correct server is listed in the homeMTA and msExchHomeServer attributes.
5 - If the attributes on the AD object are correct restart the "Archive Active Directory Connector Service".
If the AD attributes are incorrect, Using the Exchange Management Console move the users mailbox to a different database, This should refresh the attributes on the AD object and they should now reflect the correct server,
6 - Restart the "Archive Active Directory Connector Service" to pickup the updated attributes.
The following TechNet KB article explains Microsoft's reasoning on why the attribute is not updated when the database is activated on another server and also provides information on how this can be resolved in AD.
If this does not resolve the problem contact Quest Support. https://support.quest.com/