MSG
MSG is a program for sending NetBIOS, or more commonly known as "Net Send" messages from a graphical interface. In addition to being a lot easier to use than the command-line based "Net Send" in Windows, MSG allows you to do a lot of things that "Net Send" can't. ... Security features of the MSG client communication to the MSGProxyService include password protection, message integrity verification, and replay attack prevention. ... So, for instance, you can install the MSGProxyService on a web server on your company network and then have all of the same capabilities from the MSG client...
http://nighteffect.com/files/MSG_2.0/MSG_2.0_Setup.exe - 305Kb - Download - Screenshot