Action: Failed status: 4.4.7 (delivery time expired) NDR

we are located in Northern NJ and one of our costumers, some where in Malaysia, keep getting their e-mail back. It looks like the message gets to one of the servers and stays in queue and then after a period of time it gets sent back.This happens to one of our employees receiving e-mail fron this person. There is  another employee that is getting e-mails from this person without a problem. I have a Microsoft Exchange Server 5.5 with Service Pack2.
here is the message that our customer in Malaysia gets:

Return-Path: <>
Received: by mail.san.yahoo.com (6.5.017.1) id 3CBB5DA600006B14 for
userinmalaysia@dbni.net;
Sun, 21 Apr 2002 08:09:38 -0700
From: Mail Delivery Service <postmaster@mail.san.yahoo.com>
Subject: Delivery Status Notification
To: userinmalaysia@dbni.net
Date: Sun, 21 Apr 2002 08:09:38 -0700
Message-ID: <3CBB5DA600006B13@mta08.san.yahoo.com>
MIME-Version: 1.0
Content-Type: Multipart/Report; report-type=delivery-status;
boundary="=========3CBB5DA600003E7B/mail.san.yahoo.com"

This multi-part MIME message contains a Delivery Status Notification.
If you can see this text, your mail client may not be able to understand
MIME
formatted messages or DSNs (see RFC 2045 through 2049 for general MIME
information and RFC 1891 through 1894 for DSN specific information).

--=========3CBB5DA600003E7B/mail.san.yahoo.com
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit

 - These recipients of your message have been processed by the mail server:
northernNJuser@company.COM; Failed; 4.4.7 (delivery time expired)



--=========3CBB5DA600003E7B/mail.san.yahoo.com
Content-Type: Message/Delivery-Status

Reporting-MTA: dns; mail.san.yahoo.com
Arrival-Date: Thu, 18 Apr 2002 08:07:26 -0700

Final-Recipient: rfc822; northernNJuser@company.COM
Action: Failed
Status: 4.4.7 (delivery time expired)

--=========3CBB5DA600003E7B/mail.san.yahoo.com
Content-Type: Message/RFC822

Return-Path: <malaysiauser@dbni.net>
Received: from [161.142.100.86] by mail.san.yahoo.com with HTTP; Thu, 18
Apr 2002 08:07:25 -0700
Date: Thu, 18 Apr 2002 23:07:25 +0800
Message-ID: <3CBB5DA90000342C@mta08.san.yahoo.com>
From: "user" <malaysiauser@dbni.net>
Subject: RE: Are you in the office?
Reply-To: malaysiauser@dbni.net
To: "northernNJuser" <northernNJuser@company.COM>
MIME-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
Could any one please tells me what this means. I am not very knowledgeable about exchange and i will appreciate any help at all. Just in case my e-mail is:
guttysg@hotmail.com
thank you