生成的电子邮件进入垃圾邮件和奇怪的标题Received:from uknown in email

可能重复：
如何避免收到的电子邮件标题：从未知和垃圾邮件

我尝试使用php和Zend_Mail从我们的服务器发送电子邮件。我使用smtp传输。这是在我的网站上订阅的确认电子邮件。但出于某种原因，我发送的电子邮件有奇怪的标题，电子邮件会进入垃圾邮件文件夹：

Message-Id: <50f41c80.67e3440a.2d32.6aabSMTPIN_ADDED_MISSING@mx.google.com>
Received: (qmail 18457 invoked from network); 14 Jan 2013 14:55:59 -0000
Received: from unknown (HELO smtp1-1.searchboxindustries.com) (username@searchboxindustries.com@207.162.215.30)
  by searchboxindustries.com with SMTP; 14 Jan 2013 14:55:59 -0000

smtp1.searchboxindustries.com应解析为207.162.215.30。为什么我有这个标题？

列表标题"Recived:from uknown"是什么意思？它能让电子邮件变成垃圾邮件吗？如何避免这个奇怪的标题，并使电子邮件避免垃圾邮件文件夹？也许我对这个域的DNS设置有一些问题？

Spf似乎还可以：

Received-SPF: pass 

设置标题的代码：

$mailer->clearFrom();
$mailer->setFrom($params['list_email'], $params['list_from_name']);
$mailer->setReplyTo($params['list_email']);
$mailer->addHeader('Sender', $params['list_email'] . '.emailname.com');                     
$mailer->setReturnPath($params['list_email'] . '.emailname.com');           
$mailer->addTo($params['email_address']);

配置传输的代码：

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

来自application.ini的电子邮件配置：

email.name  = emailname.com
email.server = emailserver.com
email.username = email@address.com
email.password = password
email.auth = plain
email.port = 999
email.from_address = "address@email.com"
email.from_name = "Mailable";