C#.Net Outlook 2003 automation (programmatically) with Office.Interop.Outlook

I have my outlook 2003 configured with multiple mailbox on my local machine.
I want to specify the mailbox and server (Exchange server mail box)
to connect and then save the mailitems(from Inbox or any other folder)
based on a filter to a*.msg file.
I want to achieve this using only one Interop dll if this is possible.

Tried so far:
I have tried using both Outlook 11.0 object library (Microsoft.Office.Interop.Outlook)
and Interop.MAPI dll but have not been successful to connect to a different
mailbox and save to *.msg file using only Interop.Outlook or Interop.MAPI.

Using Microsoft.Office.Interop.Outlook:
I have been able to save the defaultfolder(Inbox) to *.msg files
but I want to change the default mailbox to a second mailbox like
username2 instead of default mailbox username1.
How do I accomplish this using automation from C#.Net using Microsoft.Office.Interop.Outlook?

Other Workaround using Interop.MAPI dll:
I have been able to connect using the Session.Logon of the interop.MAPI dll
but the mapi dll object model does not allow the messages to be saved to *.msg file.
Any workaround using Interop.MAPI dll?

Any ideas/suggestions are welcome.