Microsoft Office Outlook or Outlook is a personal information manager from Microsoft. The 2007 version is available both as a separate application as well as a part of the Microsoft Office suite.

Although often used mainly as an e-mail application, it also includes a Calendar, Task Manager, Contact Manager, note taking, a journal and web browsing.

It can be used as a stand-alone application, but can also operate in conjunction with Microsoft Exchange Server and Microsoft Office SharePoint Server to provide enhanced functions for multiple users in an organization, such as shared mailboxes and calendars, Exchange public folders, SharePoint lists and meeting time allocation. There are also many 3rd party add-on applications that integrate Outlook with devices and other software such as BlackBerry mobile phones and Skype internet communication software. Developers can also create their own custom software that works with Outlook and Office components using Microsoft Visual Studio. In addition, Windows Mobile devices can synchronize almost all Outlook data to Outlook Mobile.

Outlook Express

Outlook Express is an e-mail/news client that was included with Internet Explorer versions Internet Explorer 4.0 through 6.0. As such, it was also bundled with several versions of Microsoft Windows, from Windows 98 to Windows XP, and was available for Windows 95 and Mac OS 9. In Windows Vista, Outlook Express is replaced with Windows Mail. Windows Live Mail has since been released as the successor to Outlook Express and Windows Mail. Microsoft Entourage, sold as part of Microsoft Office for Macintosh, has replaced the Macintosh version.

Outlook Express is a different application from Microsoft Office Outlook. The two programs do not share a common codebase, but do share a common architectural philosophy. The similar names lead many people to incorrectly conclude that Outlook Express is a stripped-down version of Microsoft Office Outlook. Outlook Express uses the Windows Address Book to store contact information and integrates tightly with it. On Windows XP, it also integrates with Windows Messenger.