When you configure journaling mailboxes on a Microsoft Exchange Server 2010 Mailbox server, the Exchange Server 2010 Hub Transport server may take longer than expected to deliver messages to the Journal mailbox. Additionally, applications that access the journal mailbox may experience performance issues..
This issue occurs if the Exchange Server 2010 Hub Transport server performs Conversation Threading against a high-volume journaling mailbox while messages are delivered.
To resolve this issue, install the following update rollup package:
2608646 Description of Update Rollup 6 for Exchange Server 2010 Service Pack 1
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about journaling, visit the following Microsoft website: