Proxy server interaction with password protected URLs?

I've been setting up URL's that refer to FTP accounts which require a
password, the URL's are of the form (for example) :

ftp://user@ftp.race.analysys.co.uk/user_dir/

This allows us to build a nice interface to files which require a simple
password to retrieve them.  On selecting this URL, the client prompt's the
user for their password, and then lets them into the FTP server.

This works well, but some users never get prompted for the password.  This
appears to be the case when they are accessing our site through a proxy
server.  In this case, they just get the reply :

Can't Access Document: ftp://user@ftp.race.analysys.co.uk/user_dir/
Reason: FTP-server replies: User user cannot log in.

I know very little about proxy servers, but this worries me.
Will they block this kind of request by default, or is it a configuration
issue at the proxy server end?
Is this a general issue with accesses that require user-id and passwords, or
is it only an issue for this type of FTP url?

Jim Warwick @ Analysys

PS: We're running the EMWAC HTTP server on a NT 3.5 platform and also using
the shipped MS FTP server on the same machine.

Received on Friday, 26 May 1995 07:10:37 UTC