GMail显示纯文本电子邮件，而不是HTML [英] GMail displays plain text email instead HTML
问题描述
我的Rails 3应用程序以纯文本和HTML格式发送电子邮件。我已经使用RoundCube和Squirrel Mail客户端在本地进行了测试，他们都显示HTML版本与图像，链接等。另一方面，GMail选择纯文本格式。任何想法是什么原因导致的？
My Rails 3 application sends out emails in both plain text and HTML formats. I have tested it locally using RoundCube and Squirrel Mail clients and they both display HTML version with images, links, etc. GMail on the other hand chooses plain text format. Any idea what's causing this?
Delivered-To: test@gmail.com
Received: by 10.42.166.2 with SMTP id m2cs16081icy;
Thu, 3 Mar 2011 17:01:48 -0800 (PST)
Received: by 10.229.211.138 with SMTP id go10mr1544841qcb.195.1299200507499;
Thu, 03 Mar 2011 17:01:47 -0800 (PST)
Return-Path: <info@example.com>
Received: from beta.example.com (testtest.test.com [69.123.123.123])
by mx.google.com with ESMTP id j14si1690118qcu.136.2011.03.03.17.01.46;
Thu, 03 Mar 2011 17:01:46 -0800 (PST)
Received-SPF: neutral (google.com: 69.123.123.123 is neither permitted nor denied by best guess record for domain of info@example.com) client-ip=69.123.123.123;
Authentication-Results: mx.google.com; spf=neutral (google.com: 69.123.123.123 is neither permitted nor denied by best guess record for domain of info@example.com) smtp.mail=info@example.com
Received: from localhost.localdomain (localhost [127.0.0.1])
by beta.example.com (Postfix) with ESMTP id F3C273A3EC
for <test@gmail.com>; Fri, 4 Mar 2011 01:01:45 +0000 (UTC)
Date: Fri, 04 Mar 2011 01:01:45 +0000
From: info@example.com
To: test@gmail.com
Message-ID: <4d7039f9e9d3e_3449482ab7831658@test.mail>
Subject: Your example account was activated.
Mime-Version: 1.0
Content-Type: multipart/alternative;
boundary="--==_mimepart_4d7039f9e6967_3449482ab7831370";
charset=UTF-8
Content-Transfer-Encoding: 7bit
----==_mimepart_4d7039f9e6967_3449482ab7831370
Date: Fri, 04 Mar 2011 01:01:45 +0000
Mime-Version: 1.0
Content-Type: text/html;
charset=UTF-8
Content-Transfer-Encoding: 7bit
Content-ID: <4d7039f9e95ed_3449482ab7831519@test.mail>
<html>
<head>
<meta content="text/html; charset=UTF-8" http-equiv="Content-Type" />
</head>
<body>
<p><a href="http://example.com/"><img border="0" src="http://example.com/images/logo.png" alt="example logo" /></a></p>
<p>Congratulations, Test!</p>
<p>
Your <a style="text-decoration:none;color:#ef4923;" href="http://example.com/">example</a> account was activated.
</p>
</body>
</html>
----==_mimepart_4d7039f9e6967_3449482ab7831370
Date: Fri, 04 Mar 2011 01:01:45 +0000
Mime-Version: 1.0
Content-Type: text/plain;
charset=UTF-8
Content-Transfer-Encoding: 7bit
Content-ID: <4d7039f9e8b0e_3449482ab78314b7@test.mail>
Congratulations, Test!
Your example.com account was activated.
----==_mimepart_4d7039f9e6967_3449482ab7831370--
推荐答案
尝试切换消息部分的顺序，将HTML部分放在纯文本部分之后。
Try switching the order of the parts of the message, putting the HTML part after the plain-text part. It might work :).
注意：我现在不记得我在哪里读了（或者如果我确定甚至
做了），但是切换可能有帮助的原因是因为我认为消息中的
首选部分可能是最后一部分。
NOTE: I cannot remember now where I read this (or if I for sure even did), but the reason switching might help is because I think the preferred part of the message may be the last part.
更新：我发现一个地方说，多部分MIME消息中的部分应该按照不断增加的偏好顺序 - 这里，在第7.2.3节（编辑：最新版本 here ;感谢 @ALEXintlsos ！），从第三到最后一段开始。
Update: I found a place where it says that parts in a multipart MIME message should be in order of increasing preference -- here, in section 7.2.3 (edit: latest version here; thanks @ALEXintlsos!), starting with the third to last paragraph.
更新：这是7.2.3节的引用（见< a href =https://stackoverflow.com/help/referencing> https：// stackoverf low.com/help/referencing ）：
Update: Here is a quote of section 7.2.3, (see https://stackoverflow.com/help/referencing):
7.2.3 The Multipart/alternative subtype
The multipart/alternative type is syntactically identical to multipart/mixed,
but the semantics are different. In particular, each of the parts is an
"alternative" version of the same information. User agents should recognize
that the content of the various parts are interchangeable. The user agent
should either choose the "best" type based on the user's environment and
preferences, or offer the user the available alternatives. In general, choosing
the best type means displaying only the LAST part that can be displayed. This
may be used, for example, to send mail in a fancy text format in such a way
that it can easily be displayed anywhere:
From: Nathaniel Borenstein <nsb@bellcore.com>
To: Ned Freed <ned@innosoft.com>
Subject: Formatted text mail
MIME-Version: 1.0
Content-Type: multipart/alternative; boundary=boundary42
--boundary42
Content-Type: text/plain; charset=us-ascii
...plain text version of message goes here....
--boundary42
Content-Type: text/richtext
.... richtext version of same message goes here ...
--boundary42
Content-Type: text/x-whatever
.... fanciest formatted version of same message goes here
...
--boundary42--
In this example, users whose mail system understood the "text/x-whatever"
format would see only the fancy version, while other users would see only the
richtext or plain text version, depending on the capabilities of their system.
In general, user agents that compose multipart/alternative entities should
place the body parts in increasing order of preference, that is, with the
preferred format last. For fancy text, the sending user agent should put the
plainest format first and the richest format last. Receiving user agents should
pick and display the last format they are capable of displaying. In the case
where one of the alternatives is itself of type "multipart" and contains
unrecognized sub-parts, the user agent may choose either to show that
alternative, an earlier alternative, or both.
NOTE: From an implementor's perspective, it might seem more sensible to reverse
this ordering, and have the plainest alternative last. However, placing the
plainest alternative first is the friendliest possible option when
multipart/alternative entities are viewed using a non-MIME- compliant mail
reader. While this approach does impose some burden on compliant mail readers,
interoperability with older mail readers was deemed to be more important in
this case.
It may be the case that some user agents, if they can recognize more than one
of the formats, will prefer to offer the user the choice of which format to
view. This makes sense, for example, if mail includes both a nicely-formatted
image version and an easily-edited text version. What is most critical, however,
is that the user not automatically be shown multiple versions of the same data.
Either the user should be shown the last recognized version or should
explicitly be given the choice.
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