Outlook Web Access through proxy

  • From: Andrea Coppini <AndreaCoppini@xxxxxxxx>
  • To: "'exchangelist@xxxxxxxxxxxxx'" <exchangelist@xxxxxxxxxxxxx>
  • Date: Wed, 20 Feb 2002 15:48:05 +0100

Hi all,

I'm running Exchange 5.5 SP4 on WinNT4 in a DMZ behind a Checkpoint VPN-1
firewall.  The server has it's own external IP and no NAT is used.

I have this challenge:
When people use Outlook Web Access from anywhere on the internet (such as
internet cafe, other company LANs, or on dial-up), everything works fine, as
long as they don't connect through a proxy.

I have noticed this to happen with every proxy server I have tried.
(Netscape, MS Proxy/ISA, WinRoute proxy).  This is what happens:

User opens web browser (IE5 or IE6 on Win2K Prof) and enters the OWA
address... Everything's fine till here.
OWA page comes up, user enters mailbox alias name, clicks on the 'click
here' text.
A blank page shows up.
The address is

The HTML code of this blank page is the following:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<META http-equiv=Content-Type content="text/html;

If I look at the proxy log, here is the line that shows up as soon as I
click on 'Click Here':
192.168.x.xxx -- [20/feb/2002:15:45:12 +0100] "GET
HTTP/1.1" 401 0

The '401' is the returned error code, which is 'access denied'... Although
I'm never asked for logon credentials..

Any ideas?

Mr. Andrea Coppini
+49 163 5 ANDREA (263732)


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