At next week's CalConnect meeting in Utah (brrrr... but thanks Novell for hosting), I suspect one of the topics will be whether it's possible to write some kind of plugin for Outlook so that it can talk to calendar servers other than Exchange. Naturally one obvious approach is to write a generic CalDAV plugin for Outlook, and this kind of thing would make it much easier for many organizations to migrate to a standards-based approach.

The technical barriers are daunting. Outlook doesn't seem to have been designed for this kind of plugin at all. Such a plugin might have to use undocumented APIs even to work at all, and then naturally have lots of code to handle changes in those APIs from release to release. Some embryonic work is in progress at OpenConnector if anybody wants to jump right in, or I can put people in touch with each other so email me. At this point, amongst the group of people I've been talking to, we're not even convinced we have a decent approach outlined (so input from MAPI experts is particularly welcome) let alone how much work it would be. But we're starting to talk.