I'm developing a small add-in for Outlook 2010 using the Microsoft.Office.Interop.Outlook assembly. As part of my add-in, I'd like to be able to determine the date/time a mail item was last marked read or flagged for follow-up.
I thought that the LastModificationTime property of the Microsoft.Office.Interop.Outlook.MailItem class might be updated whenever an item is read/unread/flagged/unflagged but it seems this property never changes. I've tried checking using both the exposed property and the underlying MAPI property:
Item.LastModificationTime
Item.PropertyAccessor.GetProperty("http://schemas.microsoft.com/mapi/proptag/0x30080040")
I can't seem to find any good documentation on the properties that are available via the PropertyAccessor so I'm not sure if the timestamp property I'm looking for even exists. The MSDN documentation on properties lists namespaces I could use but none of the properties within those namespaces.
I know that I could hook into events of the Outlook object model to manually keep track of reading and flagging activity but I would prefer to use a standard property of the mail message if one exists.