This article describes why Microsoft Outlook requires the installation of Microsoft Outlook Express.

Outlook does not run without Outlook Express installed because Outlook shares files with Outlook Express. The shared functionality between Outlook and Outlook Express includes the following key components:

•	Management of Internet Accounts
•	Use of SMIME
•	News Reader

For additional information about the issues that you may encounter if Outlook Express is not installed, please see the following articles in the Microsoft Knowledge Base: Microsoft does not support the use of Outlook 2002 without Outlook Express installed.