Firstly, you can read the PR_LAST_VERB_EXECUTION_TIME (look at messages with
MFCMAPI or OutlookSpy to see what is available).
Secondly, when you reply to /forward a message, Outlook takes the value of
PR_CONVERSATION_INDEX from the parent message and adds 5 bytes to it. You
can use that to figure out the relationships betweeen the messages in a
folder and the replies/forwards in the Sent Items folder.
Dmitry Streblechenko (MVP)
http://www.dimastr.com/
OutlookSpy - Outlook, CDO
and MAPI Developer Tool