I am looking for info on the contents and format of the binary
attachement used in the emails sent to and from network@blackberry.net
by the Backberry desktop redirector.

I need enough info to build a replacement for the redirector that can
send and recieve emails to and from the handheld using the
network@blackberry.net signaling system.

bigjosh-ga,

I don't have all the information I needed to answer this question. 
First, let me point out that RIM has been pretty defensive of these
specifications.  Good Technology built a replacement for the
Redirector AFAIK:

http://www.good.com/

There is also some information here at the Operation WhiteBerry site:

http://www.freeprotocols.org/LEAP/Manifesto/article/OperationWhiteberry/split/node7.html

A law firm has done some forensic research on the BlackBerry, which
includes pointers to some hidden functions and the SDK:

http://www.rh-law.com/ediscovery/Blackberry.pdf

Wish I could have been of more help!

--arimathea-ga