使用 Python 解析电子邮件

Question

我正在编写一个 Python 脚本来处理从Procmail 返回的电子邮件。正如question 中所建议的那样，我正在使用以下 Procmail 配置：

:0:
|$HOME/process_mail.py

我的 process_mail.py 脚本正在通过标准输入接收一封电子邮件，如下所示：

From hostname Tue Jun 15 21:43:30 2010
Received: (qmail 8580 invoked from network); 15 Jun 2010 21:43:22 -0400
Received: from mail-fx0-f44.google.com (209.85.161.44)
by ip-73-187-35-131.ip.secureserver.net with SMTP; 15 Jun 2010 21:43:22 -0400
Received: by fxm19 with SMTP id 19so170709fxm.3
for <username@domain.com>; Tue, 15 Jun 2010 18:47:33 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.103.84.1 with SMTP id m1mr2774225mul.26.1276652853684; Tue, 15
Jun 2010 18:47:33 -0700 (PDT)
Received: by 10.123.143.4 with HTTP; Tue, 15 Jun 2010 18:47:33 -0700 (PDT)
Date: Tue, 15 Jun 2010 20:47:33 -0500
Message-ID: <AANLkTikFsIjJ3KYW1HJWcAqQlGXNiXE2YMzrj39I0tdB@mail.gmail.com>
Subject: TEST 12
From: Full Name <username@sender.com>
To: username@domain.com
Content-Type: text/plain; charset=ISO-8859-1

ONE
TWO
THREE

我正在尝试以这种方式解析消息：

>>> import email
>>> msg = email.message_from_string(full_message)

我想获取“发件人”、“收件人”和“主题”等消息字段。但是，消息对象不包含任何这些字段。

我做错了什么？

Answer 1

我自己回答。

我在构建消息的代码中发现了一个错误。它在某些行之间添加换行符，从而阻止解析器正常工作。

Answer 2

看起来你的换行符没有在附加行前加上空格，根据RFC 2822 §2.3.2，这是非法的：

每个标题字段在逻辑上都是单行字符，包括
字段名称、冒号和字段正文。为了方便
但是，为了处理每行 998/78 个字符的限制，
标头字段的字段主体部分可以拆分为多个
线表示；这称为“折叠”。一般规则是
只要这个标准允许折叠空白（不是
简单的 WSP 字符），可以在任何 WSP 之前插入 CRLF。对于
比如头域：

    Subject: This is a test

可以表示为：

    Subject: This
     is a test

它应该看起来像这样：

From hostname Tue Jun 15 21:43:30 2010
Received: (qmail 8580 invoked from network); 15 Jun 2010 21:43:22 -0400
Received: from mail-fx0-f44.google.com (209.85.161.44)
    by ip-73-187-35-131.ip.secureserver.net with SMTP; 15 Jun 2010 21:43:22 -0400
Received: by fxm19 with SMTP id 19so170709fxm.3
    for <username@domain.com>; Tue, 15 Jun 2010 18:47:33 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.103.84.1 with SMTP id m1mr2774225mul.26.1276652853684; Tue, 15
    Jun 2010 18:47:33 -0700 (PDT)
Received: by 10.123.143.4 with HTTP; Tue, 15 Jun 2010 18:47:33 -0700 (PDT)
Date: Tue, 15 Jun 2010 20:47:33 -0500
Message-ID: <AANLkTikFsIjJ3KYW1HJWcAqQlGXNiXE2YMzrj39I0tdB@mail.gmail.com>
Subject: TEST 12
From: Full Name <username@sender.com>
To: username@domain.com
Content-Type: text/plain; charset=ISO-8859-1

ONE
TWO
THREE

Answer 3

您必须确保线条不会被意外损坏（如上所示，但很难说这是否是复制粘贴问题）——带有完整的消息，例如：

Received: (qmail 8580 invoked from network); 15 Jun 2010 21:43:22 -0400
Received: from mail-fx0-f44.google.com (209.85.161.44) by ip-73-187-35-131.ip.secureserver.net with SMTP; 15 Jun 2010 21:43:22 -0400
Received: by fxm19 with SMTP id 19so170709fxm.3 for <username@domain.com>; Tue, 15 Jun 2010 18:47:33 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.103.84.1 with SMTP id m1mr2774225mul.26.1276652853684; Tue, 15 Jun 2010 18:47:33 -0700 (PDT)
Received: by 10.123.143.4 with HTTP; Tue, 15 Jun 2010 18:47:33 -0700 (PDT)
Date: Tue, 15 Jun 2010 20:47:33 -0500
Message-ID: <AANLkTikFsIjJ3KYW1HJWcAqQlGXNiXE2YMzrj39I0tdB@mail.gmail.com>
Subject: TEST 12
From: Full Name <username@sender.com>
To: username@domain.com
Content-Type: text/plain; charset=ISO-8859-1

ONE
TWO
THREE

然后

msg = email.message_from_string(msgtxt)
print msg['Subject']

根据需要打印TEST 12。