将PHPMailer与SMTP一起使用，我的VPS（由phpwebhosting托管的mydomain.com）发送了以下电子邮件，好像它来自我的Comcast帐户（jane.doe@comcast.net）到我的Gmail电子邮件（john.doe @） gmail.com），Gmail将其标记为垃圾邮件。
查看电子邮件标题，如何确定电子邮件客户端可能将电子邮件标记为垃圾邮件？
Delivered-To: jane.doe
Received: by 10.28.7.197 with SMTP id 188csp518471wmh;
Fri, 8 May 2015 06:51:39 -0700 (PDT)
X-Received: by 10.43.17.135 with SMTP id qc7mr4244827icb.14.1431093098853;
Fri, 08 May 2015 06:51:38 -0700 (PDT)
Return-Path: <john.doe@comcast.net>
Received: from smtp1.phpwebhosting.com (smtp1.phpwebhosting.com. [145.242.148.75])
by mx.google.com with SMTP id ag10si4096698icc.25.2015.05.08.06.51.38
for <jane.doe>;
Fri, 08 May 2015 06:51:38 -0700 (PDT)
Received-SPF: neutral (google.com: 145.242.148.75 is neither permitted nor denied by domain of john.doe@comcast.net) client-ip=145.242.148.75;
Authentication-Results: mx.google.com;
spf=neutral (google.com: 145.242.148.75 is neither permitted nor denied by domain of john.doe@comcast.net) smtp.mail=john.doe@comcast.net;
dmarc=fail (p=NONE dis=NONE) header.from=comcast.net
Received: (qmail 29774 invoked from network); 8 May 2015 13:51:37 -0000
Received: from unknown (HELO test.sites.mydomain.com) (outgoing@mydomain.com@145.242.134.91)
by smtp1.phpwebhosting.com with (DHE-RSA-AES256-SHA encrypted) SMTP; Fri, 08 May 2015 09:51:37 -0400
Date: Fri, 8 May 2015 06:51:36 -0700
To: Jane Doe <jane.doe>
From: John Doe <john.doe@comcast.net>
Reply-To: john.doe@comcast.net
Subject: Mydomain Password for Test Site
Message-ID: <fa1b444df47091d2ca100f40d93b14cc@test.sites.mydomain.com>
X-Priority: 3
X-Mailer: PHPMailer 5.2.9 (https://github.com/PHPMailer/PHPMailer/)
MIME-Version: 1.0
Content-Type: multipart/alternative;
boundary="b1_fa1b444df47091d2ca100f40d93b14cc"
Content-Transfer-Encoding: 8bit
--b1_fa1b444df47091d2ca100f40d93b14cc
Content-Type: text/plain; charset=us-ascii
Hello Jane,
I have added you to our Mydomain sales tracking and bid solicitation tool.
Your username is: jane.doe.
Click the following link within 24 hours to set your password: https://test.sites.mydomain.com/index.php?cid=25&task=display_p&t=28dba87d5fb8062e40a69f0192660471
Thank you
--b1_fa1b444df47091d2ca100f40d93b14cc
Content-Type: text/html; charset=us-ascii
<p>Hello Alvin,</p>
<p>I have added you to our Mydomain sales tracking and bid solicitation tool.</p>
<p>Your username is: jane.doe.</p>
<p>Click the following link within 24 hours to set your password: <a href="https://test.sites.mydomain.com/index.php?cid=25&task=display_p&t=28dba87d5fb8062e40a69f0192660471">https://test.sites.mydomain.com/index.php?cid=25&task=display_p&t=28dba87d5fb8062e40a69f0192660471</a></p>
<p>Thank you</p>
--b1_fa1b444df47091d2ca100f40d93b14cc--
答案 0 :(得分：1)
没有万无一失的方法可以说明为什么Gmail会将电子邮件标记为垃圾邮件。从发件人的角度来看，垃圾邮件过滤器通常是黑盒子，因为只有那些了解内部工作并且可以访问日志的人才能确定某些电子邮件发生了什么。标记的原因几乎可以是任何内容，例如违反发件人域的策略，IP信誉差，使用的链接信誉差，垃圾邮件的相似性，标准合规性差等等。有时也没有单一的理由。
并不是说你无法做出有根据的猜测。在这种特殊情况下，您将以comcast.net用户的名义发送电子邮件，但您完全绕过Comcast服务器。 Comcast制定了SPF和DMARC政策，虽然康卡斯特的SPF政策评估不允许或不允许smtp1.phpwebhosting.com（SPF＆＃34;中立＆＃34;结果），但DMARC结果是Gmail正在变得失败＆＃34;。 Comcast的DMARC政策不是标记未通过电子邮件验证的电子邮件（但仅报告它们），但我仍然认为这是一个不好的预兆。尝试通过授权的Comcast服务器发送电子邮件，或使用您自己的From:和Return-Path域名来查看是否可以避免被标记为垃圾邮件。