Outlook Express

Outlook Express was an e-mail and news client, originally released as Microsoft Internet Mail and News with Internet Explorer 3 in mid-1996. With the release of Internet Explorer 4, the program was improved and renamed to Outlook Express - it was included with Windows under that name since Windows 98. It was also available for Windows 3.x, Windows 95, Windows NT 3.51, and Windows NT 4.0. It was discontinued in favor of Windows Mail found in Windows Vista, which was itself then replaced with Windows Live Mail with the release of Windows 7, and later with a new modern app in Windows 8 and 10.

People often confuse it with Microsoft Outlook, a similar program bundled with Microsoft Office since Office 97, and hence think Outlook Express is a stripped-down version of Microsoft Outlook. However, that is not the case as the two programs don't share a common code base.

Pre-release
An early version of Microsoft Internet Mail and News, codenamed "Athena PIM" is included in Windows Nashville build 999.

Microsoft Internet Mail and News 1.0
Microsoft Internet Mail and News was initially released in mid-1996 with Internet Explorer 3.

Microsoft Internet Mail and News 2.0
Microsoft Internet Mail and News 2.0 was released later in 1996.

Outlook Express 4.0
Outlook Express 4.0 was the first version to carry the Outlook Express branding as part of Internet Explorer 4 in 1997.

Outlook Express 5.0
Outlook Express 5.0 was released in June 1999 and was bundled with Internet Explorer 5.0/Windows 98 Second Edition.

Outlook Express 5.01
Outlook Express 5.01 was released in February 2000 and bundled with Internet Explorer 5.01/Windows 2000.

Outlook Express 5.5
Outlook Express 5.5 was released in June 2000 and bundled with Internet Explorer 5.5/Windows Me.

Outlook Express 6.0
Outlook Express 6.0 was released in 2001 and bundled with Windows XP.

Outlook Express 7.0
Outlook Express 7.0 was seen in pre-release builds of Windows Longhorn (Vista), which would indicate that Windows Vista was to have Outlook in the final RTM build, however, in 2005 Outlook Express 7.0, along with the WinFS feature heavily needed for it was both scrapped and replaced with Windows Mail, which has a similar layout. You can find Windows Mail in Windows 7 pre-releases, though in later builds, it was intentionally broken. Windows 7 got Windows Live Mail instead. Windows Mail should not be confused with the Windows Mail present on 8 and 10 systems.

Replacement
As stated above, Outlook 7.0 was scrapped from Windows Vista and replaced with Windows Mail. This was included in many Windows 7 preview builds, though in later builds, it was intentionally broken. This was replaced in the final RTM build with Windows Live Mail, also downloadable for Windows XP, Vista, 8, 8.1, and 10 machines. In Windows 8, 8.1, and 10, Microsoft reused the Windows Mail name for a modern mail app.