I have a contact management application written in Delphi which has a “Sync with Outlook” feature that I developed 10 years ago. Now, I’m going back to add some features and fix some bugs. This sync feature uses the Outlook object model to get started, but it has an optional mode called “Use MAPI Enhancements” where it uses pure MAPI to speed up how it looks for changes, and it allows notes to be synced w/ RTF instead of just plain text.

I'm wondering if supporting two parallel paths of execution is a good idea or not.

If I went with all MAPI, I believe I'd avoid some security prompts, and I'd avoid situations where anti-virus has "script-blocking" features which block my app from connecting to Outlook. But I believe that on the down side, my 32-bit app would not be able to to connect with 64-bit Outlook 2010 using MAPI. And I wonder about the future of MAPI in general.

If I stick with the Outlook object model, will my 32-bit app be able to connect to the Outlook object model (since it's out of process COM)? If so, this is a compelling reason to keep my Outlook object model execution path in place. But if not, and if my app needs to be compiled for x64, then why not just go with pure MAPI?