This issue seems to occur with folders that were imported from another service (IMAP, etc.) or an older version of Outlook. The workaround is to re-create the folder in Exchange 2010 (or Office 365) and then move data to it from the older folder.
Article ID: 786, Created: November 11, 2013 at 8:30 PM, Modified: August 12 at 4:03 PM