Outlook Express (the "server") does not expose a COM interface, but Outlook 2000 does (true?). Even in the case of the former, [L1 ] apparently offers a way to hack COM (also see vbaoutl.hlp on msdn.microsoft.com).
In March 2004, Melissa Schrumpf posted an interesting unarchived follow-up which explained "Outlook has the ability to run an external program when new mail is received. Using a COM extension, an external script can access the INBOX. For example code, the original poster can have a look at:
http://www.geocities.com/m_schrumpf/tcl/index.html 20121001: broken link
And scroll down to the IPC section...
outlook export all - Use TCOM to export Outlook folders to the filesystem. Useful for dumping PST files to a directory. Recurses directories. Saves attachments. If attachments are Outlook MSG files, opens and exports them and their attachments.
If you can do that much, you can open whatever is saved out using open and process it however you like. Additionally, you can grab the text of the message without saving it out to filesystem. It's a property or method of the message object, I believe. I would also recommend:
com tree - A COM object browser using TCOM and the tree widget (tree.tck by D. Richard Hipp). Extremely useful in poking around in COM object structures. Has the ability to execute methods within the structure being browsed."
The Wiki page tcom Allows Emacs as Editor for MS Outlook shows how to grab the text of a currently open Outlook message.
The Using Outlook Web Access (OWA) to access an Exchange server page shows how OWA can be used from Tcl to access an Exchange server and even synchronize other applications (like KNotes) with Exchange. This now also includes an IMAP-to-OWA proxy to allow access to email on an exchange server using OWA for IMAP clients.
I feel sorry for anyone that has to code an Outlook integration. Good luck with the automation security popup warnings.