Sorry, I should have clarified a bit. Simple MAPI as implemented by Outlook Express and Outlook (Extended MAPI), which allows other programs, in this case I have Maximizer Enterprise in mind, to interface with it and allows users of the app to send emails directly from the app without opening Outlook Express or Outlook and composing a new email.
Maximizer is a customer relationship management suite with its own contacts db similar to other such programs and users are used to emailing contacts from within Maximizer. The sent emails are automatically stored in the Outlook Express/Outlook 'sent items' folder, which is advantageous over using an SMTP server directly to send email where sent items aren't saved and the user no longer has all their emails saved under one account. | 
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