我正在审查我正在使用的应用程序的邮件发送服务的设置（该服务是名为Mandrill的mailchimp收购）。
我想确定一下，当我从这个服务向我自己（gmail.com）发送一个testing邮件时， 邮件服务器之间的stream量是否使用TLS。 我可以访问发送给我的电子邮件（我已经在下面添加了标题）。
我打算问供应商他们是否支持这个function，但是我也想知道是否可以validation他们亲自告诉我的。
Delivered-To: [email protected] Received: by 10.79.123.142 with SMTP id k136xxxxxxxxxxxx; Tue, 5 Jul 2016 07:29:11 -0700 (PDT) X-Received: by 10.37.97.11 with SMTP id v11mxxxxxxxxxxxx.36.14nnnnnnnnnnn; Tue, 05 Jul 2016 07:29:11 -0700 (PDT) Return-Path: <[email protected]> Received: from mail180-123.mandrillapp.com (mail180-123.mandrillapp.com. [abcd]) by mx.google.com with ESMTPS id mmmmmmmmmmm.nnn.2016.07.05.07.29.11 for <[email protected]> (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 05 Jul 2016 07:29:11 -0700 (PDT) Received-SPF: pass (google.com: domain of [email protected] designates abcd as permitted sender) client-ip=abcd; Authentication-Results: mx.google.com; dkim=pass [email protected]; dkim=pass [email protected]; spf=pass (google.com: domain of [email protected] designates abcd as permitted sender) [email protected]; dmarc=fail (p=NONE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; s=mandrill; d=mail180-123.mandrillapp.com; h=From:Sender:Subject:Reply-To:To:Message-Id:Date:MIME-Version:Content-Type; [email protected]; bh=xxxxxxxxxxxxxxxxxxxxxxx+8fQ=; b=n+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/xxxxxxxxxxxxxxxxxxxxxxxxxxxx+Z+tSJV/zEtr xxxxxxxxx+xxxxxx+xxxxxxxxxxxxxxxxxxxxxx/xxx/xxxxxxxxxxxxxxxx/xxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxx= Received: from pmta03.mandrill.prod.suw01.rsglab.com (127.0.0.1) by mail180-123.mandrillapp.com id xxxxxxxxxxxx for <[email protected]>; Tue, 5 Jul 2016 14:29:11 +0000 (envelope-from <[email protected]>) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mandrillapp.com; [email protected]; q=dns/txt; s=mandrill; t=1467728951; h=From : Sender : Subject : Reply-To : To : Message-Id : Date : MIME-Version : Content-Type : From : Subject : Date : X-Mandrill-User : List-Unsubscribe; bh=xxxxxxxxxxxxxxxxxxxxxxxx+xxxxxxxxxxxxxxxxxx=; b=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx+xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxx= From: recipient <[email protected]> Sender: recipient <[email protected]> Subject: =?utf-8?Q?Subject Return-Path: <[email protected]> Received: from [208.nnn.nnn.nnn] by mandrillapp.com id xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx; Tue, 05 Jul 2016 14:29:11 +0000 Reply-To: <[email protected]> To: ClientSeq ClientMcD <[email protected]> Message-Id: <nnnnnnnn.nnnnnnnn142911.nnnnnnnn1aadf2.nnnnnnnn@mail180-123.mandrillapp.com> Date: Tue, 05 Jul 2016 14:29:11 +0000 MIME-Version: 1.0 行中提到的TLS
Received: from [...] (mail180-123.mandrillapp.com. [...]) by mx.google.com with ESMTPS [...] (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);
很明显，从Mandrill到GMail的连接实际上是TLS保护的。
ESMTPS（安全ESMTP）被列为传输的情况也是如此，参见RFC 3848 。