This add-on precedes the Internet Mail profile for Microsoft Exchange 4.0 bundled in Windows 95. A version 2.0 was released in the end of 1996. In 1997 the program was changed and renamed as Outlook Express and bundled in Internet Explorer 4.0. The executable file for Outlook Express, msimn.exe, is a holdover from the Internet Mail and News era.
This program is also incompatible with anything newer than Windows 95.