Strange unexplainable email delivery problem?

[Brett Busch]

Okay, here's another really interesting problem:
I have a mail server that host mail for "siteblast.com", which host a
multitude of other domains as well. This mail server works fine except, when
I try to send an message to any email account that is hosted by
"earthlink.net". When I do try to send there, I get an undeliverable message
response back, which you can see below. I can send from any other domain
from the same mail server and "earthlink.net" will accept it, but not from
"siteblast.com? I have called the people over at earthlink, and they have
told me that they DO NOT block mail (maybe a spam block) across an entire
domain. I am my wits end on this problem. Does anyone have any idea why they
won't/can't accept mail from this domain?
Thanks,
Brett Busch

Your message has encountered delivery problems
to the following recipient(s):

litalien at earthlink.net <mailto:litalien at earthlink.net>
Delivery failed
550 <bbusch at siteblast.com <mailto:bbusch at siteblast.com>>... Access denied


Sent: MAIL FROM:<bbusch at siteblast.com <mailto:bbusch at siteblast.com>>
SIZE=1391
Received:550 <bbusch at siteblast.com <mailto:bbusch at siteblast.com>>... Access
denied

Here is the header info as well:

Received: by mail1 for brett
X-From_: MAILER-DAEMON  Wed Jan 17 08:30:00 2001
Return-Path: <>
Received: from non.websourcemedia.com ([209.247.122.254])
	by nemesis.insync.net (8.9.3/8.9.3) with ESMTP id IAA23562
	for <brett at insync.net>; Wed, 17 Jan 2001 08:29:59 -0600 (CST)
Resent-To: brett at insync.net
Resent-From: bbusch at siteblast.com
Resent-Message-Id: <B0000136046 at non.websourcemedia.com>
Resent-Date: Wed, 17 Jan 2001 08:45:15 -0600
To: bbusch at siteblast.com
Subject: Delivery failure (litalien at earthlink.net)
From: postmaster at uzone.com
Message-Id: <B0000136045 at non.websourcemedia.com>
Date: Wed, 17 Jan 2001 08:45:15 -0600
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
boundary="182/320/979742715/MailSite/non.websourcemedia.com"

--182/320/979742715/MailSite/non.websourcemedia.com
Content-Type: text/plain

Your message has encountered delivery problems
to the following recipient(s):

litalien at earthlink.net
Delivery failed
550 <bbusch at siteblast.com>... Access denied
And even more info:
Received: by mail1 for brett
X-From_: MAILER-DAEMON  Wed Jan 17 08:30:00 2001
Return-Path: <>
Received: from non.websourcemedia.com ([209.247.122.254])
	by nemesis.insync.net (8.9.3/8.9.3) with ESMTP id IAA23562
	for <brett at insync.net>; Wed, 17 Jan 2001 08:29:59 -0600 (CST)
Resent-To: brett at insync.net
Resent-From: bbusch at siteblast.com
Resent-Message-Id: <B0000136046 at non.websourcemedia.com>
Resent-Date: Wed, 17 Jan 2001 08:45:15 -0600
To: bbusch at siteblast.com
Subject: Delivery failure (litalien at earthlink.net)
From: postmaster at uzone.com
Message-Id: <B0000136045 at non.websourcemedia.com>
Date: Wed, 17 Jan 2001 08:45:15 -0600
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
boundary="182/320/979742715/MailSite/non.websourcemedia.com"