* MSN Messenger is an [instant messaging] service with its own proprietary protocol
   * The official client is produced by Microsoft, and is available from http://messenger.msn.com/ for Windows or the Mac
   * The servers are run by Microsoft.  Interoperation with Yahoo IM users is promised, but is not yet available to all users
   * MSN messenger is not the same as Windows Messenger, which seems to be intended for corporate intranet deployment
   * To confuse us further, Microsoft appears to be reb