We know,Good Technology and their server software can automatically append an additional HTTP header in the request with the Good Access user's email address.but Is there any way to pass along some identifing information about the user from MDS to intranet web app?
a great question! 
We find the black berries have PIN No, IMEI No., Phone No. and IP address (witch needs 3$ more per month for static IP) are unique for each black berry device，so we can use these Identifications to identify the Black Berry unit via the MDS?
Depending on the above requirement we add any of following line to the <drive:>\Program Files\Research In Motion\BlackBerry Enterprise Server\MDS\Servers\Servername\Rimpublic.property file on the BES. This will cause the MDS to send Blackberry specific HTTP headers.
application.handler.http.header=pin
One of the headers includes the PIN of the requesting device. The header is HTTP_RIM_DEVICE_ID: <pin>
application.handler.http.header=email
One of the headers includes the EMAIL of the requesting device. The header is HTTP_RIM_DEVICE_EMAIL: <Email>
Sample:
I install BB JDE in the D:\BlackBerry JDE 4.0.2 folder,and I use the PIN No for identifying the BB unit
1. open the D:\BlackBerry JDE 4.0.2\MDS\config\rimpublic.property file
2.add the following two lines into rimpublic.property file
application.handler.http.logging=true
application.handler.http.header=pin
application.handler.http.header=pin
should be add into this follow part
# [HTTP HANDLER]
........
........
application.handler.http.logging=true
application.handler.http.header=pin
..........
application.handler.http.header=pin
..........
#application.handler.http.header.domain=
3. save and exit the rimpublic.property file
you will get the "Rim-device-id:" in the server .