No.

It is possible to access most, but not all, features when using WebDAV to access MS Exchange. All features, on the other hand, is available when using Brutus or MAPI.

Well.. to be honest, only the client relevant features of MAPI has been implemented in Brutus, but those missing (which are mainly for service providers) can be implemented easily, should a requirement surface.

An argument against supporting all Exchange versions from 5.5 onwards, that I have heard, is that Exchange 5.5 is dead technology and that I might as well focus on Exchange 2000 onwards. This is far from being true. Exchange 5.5 are alive and well in many server rooms. Many organizations would really prefer to keep their Exchange 5.5 despite Microsoft discontinuing offical support.

Yes.

To be more specific... You simply can not use WebDAV if you plan on having a decent feature set and at the same time support Exchange 5.5. Exchange 5.5 has something like 40-60% of the entire Exchange market share. Ignoring that kind of a market share is not something you should do lightly.

Well.. if you are doing a windows-only application and knows nothing of CORBA, then please do use MAPI directly.

But, you should realize that there are advantages to using Brutus, even on Windows where you could otherwise use MAPI. Some of these are:

Firstly - WebDAV is going away. See e.g. this blog entry by Terry Myerson, General Manager for the Exchange Server division at Microsoft.

Secondly and simply, WebDAV is not an option if you are one of those who are still on the Exchange 5.5 platform. A lot of organisation are still on Exchange 5.5 . Using Exchange 2000/2003 will give you more of the native feature set from Outlook, but a WebDAV based client application will allways play catch-up to a MAPI or Brutus based one.

Brutus is a CORBA based wrapping of MAPI. The entirety of Extended MAPI is wrapped except those specific parts of MAPI that are directly oriented towards the Windows graphical user interface and the service provider parts.