You have some mailboxes in a Microsoft Exchange Server 2010 environment that were moved from Exchange Server 2003 or Exchange Server 2007 to Exchange Server 2010.
Some users in the environment use Microsoft Outlook in cached mode to access the mailboxes.
The Download Headers and Then Full Items option is enabled in Outlook. Or, the Download Headers option is enabled in Outlook.
You apply some retention policies to the mailboxes.
In this scenario, Outlook freezes and the size of the .ost file for each user begins to increase. Additionally, the network load in the organization is very heavy.
Note This issue does not occur if mailboxes are created by using Exchange 2010 servers.
This issue occurs because the messaging records management (MRM) applies MRM policies to all items in mailbox folders. This causes the Outlook client to synchronize all items in the mailbox to a local .ost file.
To resolve this issue, install Exchange Server 2010 Service Pack 3 (SP3) on the Exchange Server 2010 servers. For more information about Exchange Server 2010 SP3, click the following article number to view the article in the Microsoft Knowledge Base:
2808208 Description of Exchange Server 2010 Service Pack 3
After you apply this update, you need to enable the Download Full Items option in the Download Preferences menu in Outlook.
To work around this issue, use Outlook in online mode, or use the Outlook Web App.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about MRM, go to the following Microsoft website: