Outlook Express

Outlook Express, formerly known as Microsoft Internet Mail and News, is a discontinued email and news client included with Internet Explorer versions 3.0 to 6.0. As such, it was bundled with several versions of Microsoft Windows, from Windows 98 to Windows Server 2003, and was available for Windows 3.x, Windows NT 3.51, Windows 95, Mac System 7, Mac OS 8, and Mac OS 9. In Windows Vista, Outlook Express was superseded by Windows Mail.

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

Version 1.0 was released as Microsoft Internet Mail and News in 1996 following the Internet Explorer 3 release. This add-on precedes the Internet Mail profile for Microsoft Exchange 4.0 bundled in Windows 95. Version 2.0 was released at the end of 1996. Internet Mail and News handled only plain text and rich text (RTF) email, lacking HTML email.

In 1997 the program was changed and renamed to Outlook Express and bundled with Internet Explorer 4. The Windows executable file for Outlook Express, msimn.exe, is a holdover from the Internet Mail and News era. Like Internet Explorer, Outlook Express 4 can run on Mac System 7, OS 8, and OS 9.

Internet Explorer 5 required Outlook Express 5 to save Web Archive files (see MHTML).

Outlook Express 6 is the last version of the software with Outlook branding. It has a similar layout to Outlook Express 5. It was included with Windows XP.

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Builds of "Outlook Express 7" appeared in early builds of Windows Vista when in development as "Longhorn". It relied on WinFS for the management and storage of contacts and other data.