If you mean the MIME message id header, it is not guaranteed to be present.
If it is available, it will be in the PR_INTERNET_MESSAGE_ID property
(0x1035001E), accessible using Extended MAPI (C++/Delphi only), CDO 1.21,
Redemption or MailItem.PropertyAccessor in Outlook 2007

Dmitry Streblechenko (MVP)
http://www.dimastr.com/
OutlookSpy - Outlook, CDO
and MAPI Developer Tool

"Bickers" wrote in message
...
Hi,

I need to track messages in a database, but be able to handle the same
message being sent to multiple recipients (within an Exchange
environment).

I know that all messages sent to multiple recipients will have the same
MessageID value, but I can find no information as to how to retrieve it.

What I'm planning is that when a message is opened, an AddIn will check
whether the message has already been handled and if not, store info in a
database (simplistic view). When another user reads the same message, I
need
to be able to detect that it's already been handled.

Thanks for any help,

Phil.