I'm sending out emails using PHPMailer through an SMTP server that I control, and I have DKIM and SPF set up and working properly, however, when I send a test email to my gmail account it goes to the spam folder immediately and claims that my email is similar to messages detected by their spam filters.
However, if I then use Outlook to send the exact same message through the same SMTP server, it doesn't get filtered as spam.
These are the headers from an email that went to spam
Delivered-To: firstname.lastname@example.org Received: by 10.227.117.6 with SMTP id o6csp468220wbq; Thu, 16 Aug 2012 00:21:15 -0700 (PDT) Received: by 10.43.117.129 with SMTP id fm1mr196323icc.1.1345101675202; Thu, 16 Aug 2012 00:21:15 -0700 (PDT) Return-Path: <bounce+95719fab75@my_smtp_server_domain.com> Received: from mailapproved.com (mailapproved.com. [126.96.36.199]) by mx.google.com with ESMTP id s18si1547632igi.61.2012.08.16.00.21.14; Thu, 16 Aug 2012 00:21:15 -0700 (PDT) Received-SPF: pass (google.com: domain of bounce+95719fab75@my_smtp_server_domain.com designates 188.8.131.52 as permitted sender) client-ip=184.108.40.206; Authentication-Results: mx.google.com; spf=pass (google.com: domain of bounce+95719fab75@my_smtp_server_domain.com designates 220.127.116.11 as permitted sender) smtp.mail=bounce+95719fab75@my_smtp_server_domain.com; dkim=pass email@example.com Received: from ml.my_smtp_server_domain.com.com (ml.my_smtp_server_domain.com.com [18.104.22.168]) by my_smtp_server_domain.com.com (Postfix) with ESMTPA id E3CC68E057 for <firstname.lastname@example.org>; Thu, 16 Aug 2012 07:21:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=my_smtp_server_domain.com; s=server1; t=1345101672; bh=TsyHxri8hUJjEnMBm8JUJzfLs5a3ea9aRZQ15toMNyQ=; h=Date:To:From:Reply-to:Subject:List-Unsubscribe; b=hOUSOx/fN8ZwTlEp4KBAKSGRZHgH6kSj0xUeLlq8J2JGBEE2x6c2b5sh/nFwqx45T kuorzu3TsLDDMHCBLmSNLfrYWqyCzkT4Iwh1NJlCL5zm4GwYDXVrVsd+6AjJNfzPN+ W5idEJ62+MCgsMqgCd6gmpACMcqntgwgp+WcLKFc= Date: Thu, 16 Aug 2012 15:21:12 +0800 To: Me <email@example.com> From: Someone <no-reply@my_smtp_server_domain.com> Reply-to: No Reply <no-reply@my_smtp_server_domain.com> Subject: Welcome to Blah Message-ID: <firstname.lastname@example.org_smtp_server_domain.com> List-Unsubscribe: <mailto:unsubscribe@my_smtp_server_domain.com?subject=Unsubscribe>, <http://ml.my_smtp_server_domain.com.com/unsubscribe/e783daa664> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="b1_f2039f590798697bc998c686920020df"
There are two servers here: my_smtp_server_domain.com which is the SMTP server, and ml.my_smtp_server_domain.com which is a mailing app (for legit newsletters for people who have double OP'd in).
The message itself is just a simple confirmation email for a mailing list.
I don't understand how it can work when I use Outlook but fail with PHPmailer, what's different?