2.10 Invalid messages

The following message contains Japanese text in its body. The charset parameter is not specified in the Content-Type: field. So, the body should be treated as US-ASCII.

To: piglet
Subject: an invalid message
From: pooh
MIME-Version: 1.0
Content-Type: Text/Plain

Japanese comes here.

The following header is invalid as well.

From: "»³ËÜÏÂɧ" <kazu@example.net>

The string delimited by "=?" and "?=" in the above example was originally Japanese. Since the spec of mail limits the content of headers to ASCII characters, if a string whose character set is other than ASCII, is to be stored in a header, the string must be encoded with ASCII strings according to the defined rule. But it is certainly invalid to embed the ASCII strings with ‘"’. Strings surrounded by ‘"’ are treated as is. Therefore, the string between "=?" and "?=" in the example will not be decoded into Japanese.

Several mailers are careless about the spec and regularly violate these rules. The right way to do is ask the programmers of such mailers to make the programs conformant to the spec. However, since there are so many mailers of this kind around the world, Mew tries to decode as many different formats as possible. In these cases Mew displays warnings such as:

X-Mew: Charset for body is not specified.
       To: has encoded-words in quoted text.

If you want to decode messages strictly, set ‘mew-decode-broken’ to ‘nil’. This value can be toggled dynamically by ‘C-u.’ (see See section Reading Basis).

The following message is displayed as a mess since the character set specified with the charset parameter and the actual character set of its body are different.

Content-Type: Text/Plain; charset=ISO-2022-JP

Japanese text written in Shift_JIS

By using ‘C-cC-l’, the text is re-displayed with charset guessed according to a specified language, ignoring the character set specified by the charset parameter. If you type ‘C-uC-cC-l’, you can re-display the text by specifying a character set explicitly.

This document was generated by U-X61T\saito on May, 13 2008 using texi2html 1.78.