Email Delivery Failures from Hotmail and other Domains

We are having issues where some outside senders are reporting that they are getting delivery failures, including emails sent from Hotmail.  No senders from other domains have been willing or able to send us any info on what errors they see on their end.  I have run a number of outside tests, and none have reported any problems with the info on our domain or any blacklists that apply to us.

Attached is an email response one sender received from hotmail (accounts of sender and recipient have been stripped):

X-Message-Delivery: Vj0xLjE7RD0wO1NDTD05O2w9MQ==
X-Message-Info: H83ySVbTRY3xNM/zDBIivhcZDCGxRF5ac+NMJjw9meHO5GdJt08jv7fMNCTk0Wks31gRXLlsZcyK4Hx+vWTV1g==
Received: from ([]) by with Microsoft SMTPSVC(6.0.3790.4675);
       Wed, 18 Aug 2010 07:46:27 -0700
Date: Wed, 18 Aug 2010 07:46:27 -0700
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
X-DSNContext: 7ce717b1 - 1386 - 00000002 - C00402D1
Message-ID: <>
Subject: Delivery Status Notification (Failure)
Return-Path: <>
X-OriginalArrivalTime: 18 Aug 2010 14:46:27.0220 (UTC) FILETIME=[23147540:01CB3EE4]

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

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.

Content-Type: message/delivery-status

Reporting-MTA: dns;
Received-From-MTA: dns;SNT113-W47
Arrival-Date: Mon, 16 Aug 2010 07:42:48 -0700

Final-Recipient: rfc822;
Action: failed
Status: 4.4.7

Content-Type: message/rfc822

Received: from SNT113-W47 ([]) by with Microsoft SMTPSVC(6.0.3790.4675);
       Mon, 16 Aug 2010 07:42:48 -0700
Message-ID: <SNT113-W47B138F2A462EFF92073C7C19B0@phx.gbl>
Content-Type: multipart/alternative;
X-Originating-IP: []
Subject: Testing!
Date: Mon, 16 Aug 2010 10:42:48 -0400
Importance: Normal
MIME-Version: 1.0
X-OriginalArrivalTime: 16 Aug 2010 14:42:48.0836 (UTC) FILETIME=[4C163440:01CB3D51]

Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable


Content-Type: text/html; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

Who is Participating?
emwitdeptConnect With a Mentor Author Commented:
The issue turned out to be a routing issue on the firewall.  We are looking at the other issues identified to determine if we have other problems that need addressing.  Thanks to both of you for your help!
It looks like your reverse DNS is set up incorrectly.  Hotmail, and maybe other email providers, perform outbound SMTP scanning against reverse DNS lookup.  

The IP for your mailserver resolves to ""

It should resolve to

You need to contact your ISP and have them enter a reverse DNS record for your mailserver IP (since they maintain the reverse zone for your IP block)

The record should read:
emwitdeptAuthor Commented:
Thanks for the prompt reply.  I'll check that out and post an update.
Sudeep SharmaTechnical DesignerCommented:
Setting up a SPF records for your domain would also be a good idea. That would in not getting blocked by various ISP's and email service providers.

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