- 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.
Note This issue does not occur if mailboxes are created by using Exchange 2010 servers.