XBYJS is a command that instructs the www4mail server
to request that your web browser to attempt to 
dump to the browser windows, the form data as it would
have been mailed to the www4mail server. This command
uses javascript.

Example
XJSDUMP
http://www.ictp.trieste.it

NOTE: This command is useful for those web browsers that
normally cannot place form data directly into e-mail body.
This option would show the form data in the browser window
and then you can cut and paste into your e-mail writer
window.
You might have to enable support for Javascript, please verify the
options of the IE web browser.