The Outlook object model doesn't explicitly expose property you'd need for
that. If you are using Outlook 2007 you could use the
MailItem.PropertyAccessor object to look at that property using a MAPI
property tag, otherwise you'd need to use a lower level API that allows
access such as CDO 1.21 or Redemption (
www.dimastr.com/redemption).
What you'd need to look at is the PR_LAST_VERB_EXECUTED flag property.
That's a 32-bit Long (PT_LONG) where a value of 103 (EXCHIVERB_REPLYTOALL)
means ReplyAll and 102 (EXCHIVERB_REPLYTOSENDER) is Reply.
If that property isn't there then the item is there but never replied to or
forwarded.
For PropertyAccessor you'd use this DASL property tag string to get at
PR_LAST_VERB_EXECUTED (this is a tag, not an URL):
"
http://schemas.microsoft.com/mapi/proptag/0x10810003"
For when it was replied to (another property that won't be there if no
reply/forward) you would use PR_LAST_VERB_EXECUTION_TIME
("
http://schemas.microsoft.com/mapi/proptag/0x10820040"). Reading that
property if it's there gives you the time in UTC.
For Redemption you can use an RDOMail item's Fields property and the DASL
tags to access those properties, again they'd be Empty or null if not there.
For CDO 1.21 code see the topic "Set the Outlook Reply/Forward Flag" at
http://www.cdolive.com/cdo5p2.htm for a look at code that plays with
reply/replyall/forward.