The following message is considered as US-ASCII because of lack of charset. So the body is scrambled.
To: kazu Subject: Scrambled message From: Alice MIME-Version: 1.0 Content-Type: Text/Plain Japanese comes here.
Type `C-cC-l' to convert it into appropriate character set in Mule.
Also, some fields in a header are scrambled sometime.
From: "=?iso-2022-jp?B?GyRCOzNLXE9CSScbKEI=?=" <kazu@iijlab.net>
The string surrounded by "=?" and "?=" in the example above was originally Japanese. The spec of mail defines that only ASCII characters can be contained in a header. So, if a string, whose character set is other than ASCII, to be stored in a header, the string must be encoded into ASCII strings according to the defined rule. But it is certainly illegal to embed the ASCII strings with `"'. Strings surrounded by `"' is treated as is. Therefore, the string between "=?" and "?=" in the example is not decoded into Japanese.
Several mailers are careless about the spec and made mistakes of this kind. The right way to do is ask the programmers of such mailers to make the programs conformant to the spec. If you cannot wait, do as follows. This makes Mew to decode strings surrounded by "=?" and "?=" both in Summary mode and in Message mode.
(setq mew-decode-quoted t)