Subject: Accepted characters

From: "Russ Atkind" <[email-masked]>
Date: Thu, 26 Mar 1998 15:37:17 -0500

I apologize if this question is answered in an official document: I
can't find it.  When a server is said to "support a character set", does
this mean as an argument to the SEARCH command only, or is there some other
way in which a server can "support" a charset?  In particular, is there some
way for the client to indicate that it wants the strings it passes (quoted
and/or literal) to be interpreted in a certain charset or by a certain
encoding (UTF-7 or -8, for example)?
      What do the answers to these questions imply for logins, for example? 
What if a username or password contains characters that cannot be
represented as single octets?
      Thanks for the help.

Russ

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From: Mark Crispin <[email-masked]>
Date: Thu, 26 Mar 1998 12:43:57 -0800 (PST)

On Thu, 26 Mar 1998 15:37:17 -0500, Russ Atkind wrote:
> way in which a server can "support" a charset?

A supported charset (not "character set", the two are very different!) is one
that is accepted as the argument to CHARSET in SEARCH, and is recognized in
MIME body parts.  Among other things, if you search for "Beijing" in Chinese
characters, you will find all messages with the successive Chinese characters
"north" and "capital", regardless of whether the text is from the PRC (GB),
the ROC (BIG5), Japan (JIS), or Korea (KSC) and also regardless of any MIME
encoding.

Texts used in SORT and THREAD are converted to UTF-8 prior to sorting.

There may be other implications in the future.

FYI, a "character set" is a mapping from codepoints to characters.  A charset
is a encoding of text in one or more character sets.  This ranges from the
null encoding (e.g. ISO-8859-1) to very complex encodings (ISO-2022-CN).
There are many more charsets than there are character sets.

> In particular, is there some

There is a way to specify the charset in all of the commands in which it is
relevant (SEARCH, SORT, and THREAD).

> represented as single octets?

User names and passwords are ASCII.  There are no plans to change this,
especially since authentication is moving away from plaintext.  If you want
Arabic characters in your Kerberos authentication credentials, you need to
talk to the Kerberos folks.

Mailbox names are Unicode, encoded in a form called "modified UTF-7", which
represents the strings in ASCII.