BCC's are not distributed correctly

Hi All,

We have a problem with our email system, the email is setup as follows:

1- We have an email server setup at the ISP
2- We have one catchall account to recieve all the emails coming to the domain
3- We have a POP connector to retrieve the emails from the catchall account
4- The POP connector distributes the emails to Exchange 2003 Server

The Problem is:

When someone sends an email to for example: "user1@mydomain.com" with a BCC to "user2@mydomain.com" .. the email only gets delivered to "User1".

If the email is sent to "userabc@anotherdomain.com" and BCC to "user1@mydomain.com" the email gets delivered correctly to "user1".

If the email is sent to "userabc@anotherdomain.com" and BCC to "user1@mydomain.com" and "user2@mydomain.com" the email only gets delivered to "user1" !!!

When i viewed the header for an email on the ISP server before the POP connector pulls it, it was like this: (the email was sent to both "user1" and "user2" in the BCC)

====================================================
Return-Path: <ExternalEmailAddress>
Received: from blu0-omc4-s38.blu0.hotmail.com [65.55.111.177] by SPIRIT.secure-xp.net with SMTP;
   Wed, 8 Apr 2009 03:05:20 -0600
Received: from BLU118-W35 ([65.55.111.136]) by blu0-omc4-s38.blu0.hotmail.com with Microsoft SMTPSVC(6.0.3790.3959);
       Wed, 8 Apr 2009 02:06:00 -0700
Message-ID: <BLU118-W354669F2EBBF32477F275290820@phx.gbl>
Return-Path: ExternalEmailAddress
Content-Type: multipart/alternative;
      boundary="_5ca649ac-680d-46cb-b6d8-b60ac6ad5da1_"
X-Originating-IP: [89.211.169.177]
From: MyName <ExternalEmailAddress>
To: "userabc@anotherdomain.com" <userabc@anotherdomain.com>
Subject: Testing to BCC
Date: Wed, 8 Apr 2009 11:06:00 +0200
Importance: Normal
MIME-Version: 1.0
X-OriginalArrivalTime: 08 Apr 2009 09:06:00.0273 (UTC) FILETIME=[3C5DF410:01C9B829]
X-Rcpt-To: <user1@mydomain.com>
====================================================

As you can see, only "user1" appeared in the "X-Rcpt-To" header and thus the email was only delivered to "user1" while "user2" recieved nothing.

Your suggestions are highly appreciated.