Delivery Failed

Messages from Hotmail to our domain are failing intermittently. When they fail, there is no evidence they are ever reaching our servers at all.

--9B095B5ADSN=_01CDFD40A84B9F7800028F26snt0?omc3?s31.sn
Content-Type: message/delivery-status

Reporting-MTA: dns;snt0-omc3-s31.snt0.hotmail.com
Received-From-MTA: dns;SNT130-W52
Arrival-Date: Tue, 5 Feb 2013 11:00:15 -0800

Final-Recipient: rfc822;*** Email address is removed for privacy ***
Action: failed
Status: 5.7.1
Diagnostic-Code: smtp;550 5.7.1 <*** Email address is removed for privacy ***>... Relaying denied

--9B095B5ADSN=_01CDFD40A84B9F7800028F26snt0?omc3?s31.sn
Content-Type: message/rfc822

Received: from SNT130-W52 ([65.55.90.136]) by snt0-omc3-s31.snt0.hotmail.com with Microsoft SMTPSVC(6.0.3790.4675);
	 Tue, 5 Feb 2013 11:00:15 -0800
X-EIP: [emwGqVI2SjtHBeazpftCGAHEDRZwnceH]
X-Originating-Email: [*** Email address is removed for privacy ***]
Message-ID: <*** Email address is removed for privacy ***>
Return-Path: *** Email address is removed for privacy ***
Content-Type: multipart/alternative;
	boundary="_3ffe2b63-bb10-42fe-bec3-63132d5bfd0e_"
From: Finley The Dolphin <*** Email address is removed for privacy ***>
To: <*** Email address is removed for privacy ***>
Subject: About the testing
Date: Tue, 5 Feb 2013 11:00:14 -0800
Importance: Normal
MIME-Version: 1.0
X-OriginalArrivalTime: 05 Feb 2013 19:00:15.0938 (UTC) FILETIME=[08B4EA20:01CE03D3]

--_3ffe2b63-bb10-42fe-bec3-63132d5bfd0e_
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable