how to avoid email header Received: from unknown and email going to spam

Question

I try to send email from our server using php and Zend_Mail. I use smtp transport. This is confimation email of subscribing. But for some reason email that I send has strange headers and email goes to spam folder (I see them in gmail that receive letter):

 Message-Id: <[e-mail]>
    Received: (qmail 10943 invoked from network); 10 Jan 2013 10:16:22 -0000
    Received: from unknown (HELO searchboxindustries.com)  ([email protected]@207.162.215.30)

What does it mean list header "Recieved: from unknown"? Can it make email go to spam? How to avoid this strange header and make email avoid spam folder? Is there any problem with coode or maybe I have some problems with DNS settings of this domain?

Here's code for setting headers:

$mailer->setFrom($params['list_email'], $params['list_from_name']);
$mailer->setReplyTo($params['list_email']);

$mailer->addHeader('Sender', $params['list_email'] . '.searchboxindustries.com');                       
$mailer->setReturnPath($params['list_email'] . '.searchboxindustries.com');         

$mailer->addTo($params['email_address']);

Code to configure transport:

$emailConfig = $this->getOption('email');                                   
        $transport = new Zend_Mail_Transport_Smtp($emailConfig['server'], $emailConfig);
Zend_Mail::setDefaultTransport($transport);

Email config from application.ini:

   email.name  = searchboxindustries.com
   email.server = searchboxindustries.com
   email.username = user_name
   email.password = password
   email.auth = plain
   email.port = 587

Here are headers of such email:

Delivered-To: [email protected]
Received: by 10.76.94.204 with SMTP id de12csp111150oab;
        Fri, 11 Jan 2013 01:58:49 -0800 (PST)
X-Received: by 10.69.0.8 with SMTP id au8mr228881813pbd.58.1357898329423;
        Fri, 11 Jan 2013 01:58:49 -0800 (PST)
Return-Path: <[email protected]>
Received: from smtp1-1.searchboxindustries.com (mta1.searchboxindustries.com. [207.162.215.30])
        by mx.google.com with SMTP id d7si4727205paw.95.2013.01.11.01.58.48;
        Fri, 11 Jan 2013 01:58:48 -0800 (PST)
Received-SPF: pass (google.com: domain of [email protected] designates 207.162.215.30 as permitted sender) client-ip=207.162.215.30;
Authentication-Results: mx.google.com;
       spf=pass (google.com: domain of [email protected] designates 207.162.215.30 as permitted sender) [email protected]
Message-Id: <[email protected]>
Received: (qmail 21583 invoked from network); 11 Jan 2013 09:58:48 -0000
Received: from unknown (HELO searchboxindustries.com) ([email protected]@207.162.215.30)
  by searchboxindustries.com with SMTP; 11 Jan 2013 09:58:48 -0000
From: Oleg <[email protected]>
Reply-To: [email protected]
Sender: [email protected]
Return-Path: [email protected]
To: [email protected]
Subject: List1: Confirm Subscription
Date: Fri, 11 Jan 2013 04:58:48 -0500
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
MIME-Version: 1.0

Spf seems to be ok. The ip from which email is sent is not blacklisted.

Now there are changes in DNS and I have headers:

Message-Id: <[email protected]>
Received: (qmail 18457 invoked from network); 14 Jan 2013 14:55:59 -0000
Received: from unknown (HELO smtp1-1.searchboxindustries.com) ([email protected]@207.162.215.30)
  by searchboxindustries.com with SMTP; 14 Jan 2013 14:55:59 -0000

We have Reverse DNS set. 207.162.215.30 is resolved to stmp1.searchboxindustries.com. What's the problem then? I wonder what is strange format in brackets in the header Received : from unknow:

 [email protected]@207.162.215.30

Answer 1

The Received: from unknown simply means that one SMTP server receiveid it from another which did not provide reverse DNS. Typically each hop from one SMTP server to another adds one Received: header at the top of the message (except qmail, which adds two; this is visible in your example).

If you are concerned about the lack of reverse DNS, and if 207.162.215.30 is yours, then perhaps you can convince your ISP to provide reverse DNS for it. Many ISPs refuse (if you are on a "consumer" broadband plan), or will require a different hosting contract with you in order to offer this service. ("Reverse DNS" means that when somebody queries DNS for "what's the DNS name of 207.162.215.30" the answer would be "searchboxindustries.com" or perhaps another host name, but not "unknown".)

The reverse DNS lookup is usually performed based on the TCP headers, not on the text of the message. If the SMTP server receives a connection from 123.45.67.89 then it will perform reverse DNS for that address, and put the results in the Received: header it adds. In other words, the contents of your message headers or envelope headers do not affect this outcome at all.

Recipients can do whatever they want with these headers. It is unlikely that this header alone (the presence of this header, or the absence of reverse DNS information evident from the contents of it) would be sufficient for somebody to classify your message as spam, but there is really no way to control what the recipient does with this information.

If anything, your question is an indication that perhaps you should be looking at a professional service to send out these messages on your behalf, for a fee.