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Issues with Secondary SMTP (sendmail) Server

Posted on 2006-06-15
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Last Modified: 2013-12-16
I'm having some trouble with our web-generated emails (like newsletters, contact forms, etc.) are not valid due to some issues with sendmail, so they are being filtered out my spam filters. Our company's mail is handled by ElectricMail (MX records are set to inbound.electric.net). However, we need to be able to send -valid- messages from our web server (www.thedomain.com) (which runs on Fedora Core 3).

Here are the problems that the spam filters identify in the messages...

- HELO doesn't use FQDN
- Sending IP's PTR record doesn't match HELO
- Sending IP's PTR record is full of numbers (so is probably bogus as far as spam filters see the world)
- Message ID illegal (no FQDN)

Here are the headers of the message.....

Return-Path: <apache@localhost.localdomain>
Received: from localhost.localdomain (customer-reverse-entry.111.222.333.444 [111.222.333.444] (may be forged))
 by receiver-domain.com (4.13.10/4.13.10) with ESMTP id k5CFra3R024823
 for <user@receiver-domain.com>; Mon, 12 Jun 2006 11:53:38 -0400
Received: from localhost.localdomain (localhost.localdomain [127.0.0.1])
 by localhost.localdomain (4.13.10/4.13.10) with ESMTP id k5D0vpHV000975
 for <user@receiver-domain.com>; Mon, 12 Jun 2006 17:57:51 -0700
Received: (from apache@localhost)
 by localhost.localdomain (4.13.10/4.13.10/Submit) id k5D0vdmM000973;
 Mon, 12 Jun 2006 17:57:39 -0700
Date: Mon, 12 Jun 2006 17:57:39 -0700
Message-Id: <200606130057.k5D0vdmM000973@localhost.localdomain>
To: user@receiver-domain.com
Subject: Message from 1
From: user@somedomain.com
Content-type: text/html

I imagined that many of these problems might be able to be fixed by changing the hostname, and perhaps a few headers in PHP. But basically, when I change the /etc/hosts file on the web server to say...

111.222.333.444     www.thedomain.com

it starts sending any emails that are to something@thedomain.com to itself, instead of using the MX record indicated in thedomain.com (which is inbound.electric.net). This obviously is not very helpful, since nobody connects to the web server (www.thedomain.com) to retrieve their mail. I can fix this problem by taking out that line. However, the first set of problems still exists (which is what I'm looking to fix, primarily).

Some of these problems can be fixed, to a limited extent by changing headers in PHP, but many of these headers refuse to change, probably due to configuration settings. Perhaps reverse DNS is required? I'm not sure (and I'm not sure where to start with that regarding sendmail).

I've taken a look at the sendmail.cf and sendmail.mc files, but don't know where to begin on that issue, or if changing those files is part of the solution. I'm more of a web developer than a sys admin. If someone could give a few suggestions on where to start (or more detail would be -very- welcome :), it would certainly be greatly appreciated.

Thanks very much. I certainly appreciate any help.

- Jonathan


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Question by:jbulow
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pjedmond earned 320 total points
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- HELO doesn't use FQDN
- Sending IP's PTR record doesn't match HELO
- Sending IP's PTR record is full of numbers (so is probably bogus as far as spam filters see the world)
- Message ID illegal (no FQDN)

Starting at the top:

1. Check etc hosts:

Mine is:
------8X------------
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1       localhost.localdomain   localhost
192.168.1.100   bigserver bigserver.mydomain.com
------8X------------

I suspect that yours only has the localhost line?

That should solve both of the issues relating to the FQDN.

The other 2 relate to the reverse DNS (the name) of your system (as seen by the server you are sending the email to). If you don't have a fixed IP addressregistered as 'bigserver.mydomain.com' using the above example, then you will always have a problem with this. You will need to get your ISP to register this for you.

If you can't do that, then your aim should be to reduce other SPAM features to the absolute minimum in order to reduce the chance of the email being labled as spam.

HTH:)
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