High Quality Content by WIKIPEDIA articles! XMail is a free open-source POP3/ESMTP mail server for Unix and Microsoft Windows operating systems. UNlike other email servers, XMail does not require that each user have a system account, instead it uses flat-file databases to store user information. XMAil is a light-weight email server ideally suited for use in situations where other servers such as sendmail and qmail would be overkill. MIcrosoft Windows is a series of software operating systems and graphical user interfaces produced by Microsoft. MIcrosoft first introduced an operating environment named Windows in November 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces (GUIs). MIcrosoft Windows came to dominate the world's personal computer market, overtaking Mac OS, which had been introduced previously. AS of October 2009, Windows had approximately 91% of the market share of the client operating systems for usage on the Internet.