MAPI isn't used to talk to Outlook Mailboxes.. mostly because outlook doesn't have mailboxes, per se. Outlook is a program that's used to read email- in the case your describing, from a mailbox on an exchange server. MAPI is how outlook talks to the exchange server.
You would use MAPI to talk to an exchange server. Of course, there are other options.
Web Developer, PDI Inc.
NOT a Wiley/Wrox Employee