Message created by a Microsoft e-mail program, such as Outlook or Outlook Express; compatible with other programs that use Microsoft's Messaging Applications Programming Interface (MAPI).
Program(s) that open msg files
Windows: Microsoft Outlook; Priasoft MSG File Viewer and Assessor; Encryptomatic MsgViewer Pro
Information from FileInfo.com - The File Extensions Resource.
http://www.fileinfo.com/extension/msg
