I am the System Administrator for a public library system. We have our own exchange server that we use for all of our employees over several branches. It seems as though a couple of weeks ago we started having issues sending emails to both Comcast.net and AOL.com email addresses. When I send an email, the person never receives the email, and we do not get a rejection message for several days after the email is sent. I am going to put a sample email here and "xxxxx" out the personal side of things to protect the person's personal email but that shouldn't affect being able to determine what the problem is here. I have seen another post on this site for something very similar but that post seemed to have been caused by a dynamic address being used for the email server. We have public static IP addresses assigned through our router to specific private IP addresses. I will post the rejection message below and hopefully someone will be able to help me resolve this issue.
From: Mail Delivery System [mailto:MAILER-DAEMON@sophos.khcpl.org]
Sent: Monday, January 1, 2018 7:13 PM
Subject: Undeliverable: Pay Stub Date = 12/29/17
Delivery has failed to these recipients or groups:
A problem occurred during the delivery of this message to this e-mail address. Try sending this message again. If the problem continues, please contact your helpdesk.
The following organization rejected your message: mx2.comcast.net.
Diagnostic information for administrators:
Generating server: sophos.khcpl.org
mx2.comcast.net #<mx2.comcast.net #4.0.0 smtp; 421 resimta-ch2-33v.sys.comcast.net resimta-ch2-33v.sys.comcast.net Reverse DNS failure : Try again later> #SMTP#
Original message headers:
Return-Path: <firstname.lastname@example.org>Received: from sophos.khcpl.org (localhost.localdomain [127.0.0.1]) by localhost (Email Security Appliance) with SMTP id ACEC17F464_A4436C9B for <email@example.com>; Thu, 28 Dec 2017 00:11:53 +0000 (GMT)Received: from xxxxx.kokomo.lib.in.us (unknown [192.168.220.37]) by sophos.khcpl.org (Sophos Email Appliance) with ESMTP id 776D18251D_A4436C9F for <firstname.lastname@example.org>; Thu, 28 Dec 2017 00:11:53 +0000 (GMT)Received: from xxxxx.kokomo.lib.in.us ([192.168.220.37]) by xxxxx.kokomo.lib.in.us ([192.168.220.37]) with mapi id 14.03.0319.002; Wed, 27 Dec 2017 19:11:39 -0500From: Doug Workinger <email@example.com>To: "firstname.lastname@example.org" <email@example.com>Subject: Fwd: Pay Stub Date = 12/29/17Thread-Topic: Pay Stub Date = 12/29/17Thread-Index: AdN/W5I3aXgtt4DTS9ODyYjPI2JdUQAFNwR8Date: Thu, 28 Dec 2017 00:11:38 +0000Message-ID: <4348ABE1-0123-41EE-AF67-49F68E450DDB@khcpl.org>References: <13D2878E9BCDAE48912BBA9EABF4B42A98435E85@xxxxx.kokomo.lib.in.us>In-Reply-To: <13D2878E9BCDAE48912BBA9EABF4B42A98435E85@xxxxx.kokomo.lib.in.us>Accept-Language: en-USContent-Language: en-USX-MS-Has-Attach: yesX-MS-TNEF-Correlator:Content-Type: multipart/mixed; boundary="_005_4348ABE1012341EEAF6749F68E450DDBkhcplorg_"MIME-Version: 1.0
Edit: I can also message someone the static public IP address if it is absolutely needed.