为什么我可以在收到的电子邮件中看到密件抄送收件人?

为什么我可以在收到的电子邮件中看到密件抄送收件人?

我对此感到很困惑。
今天我收到一封电子邮件,其中可以看到密件抄送收件人:

在此处输入图片描述

标头:

Return-Path: xxxxxxx
Received: from xxxx ([xxxx]) by xxxxx (xxxx)
 with ESMTPS (Nemesis) id xxxxx for <xxxxx>;
 Wed, 06 May 2015 12:59:47 +0200
Received: from [xxxxx] (port=4696)
    by xxxxx with esmtp (Exim 4.82_1-5b7a7c0-XX)
    (envelope-from <xxxx>)
    id xxxxx
    for xxxxx; Wed, 06 May 2015 12:59:45 +0200
Received: from xxxxx [xxxxx] by xxxxx with xxxx(xxxxx);
 06 May 2015 10:59:45 UT
Content-Type: multipart/mixed; boundary="===============0674811891=="
MIME-Version: 1.0
From: xxxxx
To: xxxxx
bcc: bxxxx@xxxx
Date: Wed, 06 May 2015 12:59:44 +0200
Subject: Rechnung Online Kunden P
Envelope-To: <xxxx>

这怎么可能?如果 Thunderbird 正确识别了此元数据,那么它应该以正确的方式发送(而我或 Thunderbird 分别不会看到它),不是吗?

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