IIS SMTP server not able to connect to destination mail server

I have a Microsoft Windows 2003 web server running IIS 6.0 and SMTP server. I access the SMTP server in my ASP pages (via Persits Software's ASPemail) to generate outgoing mail, for a variety of reasons (form submissions, online order notifications, etc.).

Anytime a message fails to send (either from ASPemail or SMTP server), it bounces a copy of the delivery status notification message back to me, as the administrator, so I can forward the mail to the appropriate client. This often happens if someone is typing in a website submission form and mis-types their e-mail address, since SMTP server won't allow a message to go out if it has an invalid "from" address.

In general, this works fine. However, there are a few of my clients' domains which I cannot seem to get mail to send to because it says "unable to connect successfully to the destination mail server". The biggest problem for me right now is the domain kohlbp.com. I control the DNS for this domain, which has an A record mail.kohlbp.com pointing to their mail server's IP address 209.10.110.95 and MX records are pointing to mail.kohlbp.com. Their mail in general is working fine, they send and receive messages all day long, I can send and receive messages from them using my Comcast account, etc.

However, when I try to generate a message using our web server's SMTP server, I get what is pasted below (almost in its entirety). The only thing I stripped out was the body of the original message, due to privacy.

So again, in general our server appears to be sending e-mail out with no problem, and kohlbp.com's e-mail system is working, yet for some reason we cannot connect directly to them. I would love to be able to fix this, but I'm out of ideas. Would greatly appreciate some assistance! Thanks.

From: postmaster@blade4
To: info@kohlbp.com
Date: Sat, 10 Feb 2007 19:52:36 -0500
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
      boundary="9B095B5ADSN=_01C73D6BA8A5FC1600000864smtp.bbdesign.co"
X-DSNContext: 7ce717b1 - 1386 - 00000002 - C00402D1
Message-ID: <gnFZS4HIv00000590@smtp.bbdesign.com>
Subject: Delivery Status Notification (Failure)

This is a MIME-formatted message.  
Portions of this message may be unreadable without a MIME-capable mail program.

--9B095B5ADSN=_01C73D6BA8A5FC1600000864smtp.bbdesign.co
Content-Type: text/plain; charset=unicode-1-1-utf-7

This is an automatically generated Delivery Status Notification.

Unable to deliver message to the following recipients, due to being unable to connect successfully to the destination mail server.

       info@kohlbp.com




--9B095B5ADSN=_01C73D6BA8A5FC1600000864smtp.bbdesign.co
Content-Type: message/delivery-status

Reporting-MTA: dns;smtp.bbdesign.com
Received-From-MTA: dns;blade4
Arrival-Date: Thu, 8 Feb 2007 17:00:24 -0500

Final-Recipient: rfc822;info@kohlbp.com
Action: failed
Status: 4.4.7

--9B095B5ADSN=_01C73D6BA8A5FC1600000864smtp.bbdesign.co
Content-Type: message/rfc822

Received: from blade4 ([192.168.0.22]) by smtp.bbdesign.com with Microsoft SMTPSVC(6.0.3790.1830);
       Thu, 8 Feb 2007 17:00:24 -0500
From: <info@kohlbp.com>
To: info@kohlbp.com
Subject: REWARDS 2004-05 REGISTRATION
Date: Thu, 08 Feb 2007 17:00:24 -0500
Message-ID: <20070208-17002466-1f4@blade4>
MIME-Version: 1.0
Return-Path: info@kohlbp.com
X-OriginalArrivalTime: 08 Feb 2007 22:00:24.0668 (UTC) FILETIME=[88F779C0:01C74BCC]

--9B095B5ADSN=_01C73D6BA8A5FC1600000864smtp.bbdesign.co--