Durell Diary + Outlook Express versus Exchange Server + Outlook 2000, etc
Outlook Express is a fundamentally different product from the other versions of Outlook (e.g. Outlook 97, 2000, 2003 and XP) though actually they all use the same underlying “engine” to send and receive emails. It is supplied free with all versions of Windows and includes an “Address Book” for contact details.
The various other versions of Outlook (e.g. Outlook 97, 2000, 2003 and XP) integrate these two basic functions with extra facilities for handling diary appointments and tasks, and thus create a “Personal Information Manager” or PIM. However as the acronym “PIM” implies, it is a personal application not a multi-user one, so you cannot share other peoples’ contacts, check their diaries or tasks unless you also add Microsoft’s database manager called “Exchange Server”.
So the real contest is between the combinations of [Durell Diary+Outlook Express] versus [Exchange Server+Outlook 97, 2000 or 2003, etc]. Given that you’ve already purchased Durell to handle your policies, fees, or some other feature not in Outlook, then it would seem an unnecessary extravagance and extra complication to also buy and maintain Exchange Server and Outlook.
So in summary…