Capture Outlook mail?

I have a program that sends emails via outlook 2003 on my XP machine,
that I want to work when I'm not logged in.  I can't seem to get
Outlook to load as a service, so I was wondering if there is another
way.  Is it possible to intercept the emails being sent by this other
program (I can't seem to change anything with the program, so I assume
it must be using the MSO libraries to actually send the messages?)
There should be a way to write a program that will act like an outlook
'Outbox', so that I can send the messages, and run my program as a
service.  Any ideas on how to create this fake outbox?

Thanks

Dan