FTP and Proxy

I have been beating this dead horse for a while and thought I would hit it
one more time......


Scenario:

Client X has a workstation that utilizes the Proxy/Caching facilities of
ISA. Web Browsing works perfectly, however, FTP clients such as WS-FTP32 and
CuteFTP connect to the Proxy Servers port and waite for a response but
timeout waiting every time.

The Mystery:
With WinProxy 3.0 you could set up FTP clients such as WS-FTP32 as
Type="USER after login" and specify a user ID of <uid>@ftp.site.com
<ftp://ftp.site.com>  with a password for that site at port 21. The server
running Winproxy does not have to be the default route for all systems nor
is there any client software to make this work. This is not working with ISA
in Proxy only or Integrated mode. 

The Question:
Can ISA in Proxy and or Integrated mode behave this way? If so how do you
set up the server and how do you set up the client. Or is this something
that ISA just can't do and thus I am beating a dead hoarse for nothing?

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