All Wordpress PHP Mail stuff being sent to spam

Question

Every mail sent with the PHP Mail() is getting sent straight to spam (all providers e.g. gmail, yahoo, hotmail)

My IP is not blacklisted.

Here is an example of an email header that got sent to spam:

Delivered-To: jordashtalon@gmail.com
Received: by 10.229.91.149 with SMTP id n21cs189229qcm;
        Mon, 26 Dec 2011 17:43:12 -0800 (PST)
Received: by 10.43.117.194 with SMTP id fn2mr27050431icc.53.1324950190711;
    Mon, 26 Dec 2011 17:43:10 -0800 (PST)
Return-Path: <noreply@avatarthelastairbenderonline.com>
Received: from host.avatarthelastairbenderonline.com 

(host.avatarthelastairbenderonline.com. [173.199.171.80])
        by mx.google.com with ESMTPS id ut2si17526443igc.26.2011.12.26.17.43.10
        (version=TLSv1/SSLv3 cipher=OTHER);
        Mon, 26 Dec 2011 17:43:10 -0800 (PST)
Received-SPF: pass (google.com: best guess record for domain of noreply@avatarthelastairbenderonline.com designates 173.199.171.80 as permitted sender) client-ip=173.199.171.80;
DomainKey-Status: bad format
Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of noreply@avatarthelastairbenderonline.com designates 173.199.171.80 as permitted sender) smtp.mail=noreply@avatarthelastairbenderonline.com; domainkeys=neutral (bad format) header.From=noreply@avatarthelastairbenderonline.com
DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=default; d=avatarthelastairbenderonline.com;
    h=Received:Date:To:From:Subject:Message-ID:X-Priority:X-Mailer:MIME-Version:Content-Transfer-Encoding:Content-Type:X-Source:X-Source-Args:X-Source-Dir;
    b=p8We0ql3qPoF6Jk79NICVgnMedJR6xGsnBQPp0q/0h+NCY2YdtUh7ouRKNEcpAhXNr+OKzs2XWd37fn86sLcrC0tWUGXU0JUeyktyGYpNOoTeI9ImFlrD3Vt1VDQ+JXr;
Received: from host.avatarthelastairbenderonline.com ([173.199.171.80] helo=avatarthelastairbenderonline.com)
    by host.avatarthelastairbenderonline.com with esmtpsa (TLSv1:AES256-SHA:256)
    (Exim 4.69)
    (envelope-from <noreply@avatarthelastairbenderonline.com>)
    id 1RfM4K-0001Yg-Bz
    for jordashtalon@gmail.com; Mon, 26 Dec 2011 19:43:08 -0600
Date: Tue, 27 Dec 2011 01:43:08 +0000
To: jordashtalon@gmail.com
From: Avatar The Last Airbender <noreply@avatarthelastairbenderonline.com>
Subject: Test message from your WordPress blog
Message-ID: <3bfb7466ba93540ac86be00e3792e30b@avatarthelastairbenderonline.com>
X-Priority: 3
X-Mailer: PHPMailer 5.1 (phpmailer.sourceforge.net)
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain; charset="UTF-8"
X-AntiAbuse: This header was added to track abuse, please include it with any abuse report
X-AntiAbuse: Primary Hostname - host.avatarthelastairbenderonline.com
X-AntiAbuse: Original Domain - gmail.com
X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12]
X-AntiAbuse: Sender Address Domain - avatarthelastairbenderonline.com
X-Source: 
X-Source-Args: 
X-Source-Dir: 

Hi, this is the Configure SMTP plugin e-mailing you a test message from your WordPress blog.

This message was sent with this time-stamp: 2011-12-26 19:43:08

Only think I can see is it says that the DomainKey-status says bad format.

What is the domain key? and would it send emails to spam?

Can anyone tell why these emails are being sent to spam?

Even the basic Contact Form 7 Wordpress plugin is sending emails straight to spam.

Answer 1

DomainKeys Identified Mail (DKIM) lets an organization take responsibility for a message that is in transit. The organization is a handler of the message, either as its originator or as an intermediary. Their reputation is the basis for evaluating whether to trust the message for further handling, such as delivery. Technically DKIM provides a method for validating a domain name identity that is associated with a message through cryptographic authentication. (Source: http://www.dkim.org/)

Contact Form 7 plugin is sending emails to spam because internally it is also using the same SMTP mechanism to send the email originating from your host machine. Sending email from your own host is not a good idea for the problems you are facing.

You can solve this by using an SMTP server which supports DKIM. You can use one of these two options: (I am sure there are other ways as well)

1. Use Gmail as your SMTP server. (Help: http://lifehacker.com/111166/how-to-use-gmail-as-your-smtp-server) You can sign up for google apps and use your domain name with gmail as well.
2. Use amazon SES to send your emails. They recently started SMTP authentication as well. You may be charged nominally for this.