Automatic content-type insertion
leg+ at andrew.cmu.edu
Thu Dec 26 00:04:21 EST 2002
--On Monday, December 02, 2002 10:43 AM +1100 Rob Mueller
<robm at fastmail.fm> wrote:
> I'm just wondering why cyrus automatically adds a content type charset to
> every message, even if none is specified in the message itself. For
> So there's no "Content-Type" line in the message, but the bodystructure
> has given it an implicit charset of us-ascii. Now, I know that this is
> technically true, but unfortunately, there seem to be quite a few broken
> iso-2022-jp messages out there which don't actually specify the charset in
> the header. What we allow on our site is a 'default charset', which is
> used if no charset is available, which would work fine in this situation.
> Unfortunately in this case, there's no indication that the ("CHARSET"
> "us-ascii") response was auto-generated, rather than explicitly set.
It does this because that's what the IMAP spec says to do. Section 7.4.2:
> A parenthesized list that describes the [MIME-IMB] body
> structure of a message. This is computed by the server by
> parsing the [MIME-IMB] header fields, defaulting various fields
> as necessary.
> The main solutions I see are:
> 1. Remove the implicit setting of the charset if none supplied
It appears that this would conflict with the RFC.
> 2. us-ascii is a subset of most encodings anyway, so always allow
> overriding of a us-ascii charset anyway
This is probably reasonable, especially if your allowable "default
encodings" are all supersets of US-ASCII.
> 3. Do a fetch body[header.fields (Content-Type)] to see if one actually
This seems more annoying and I suspect it's not particularly fast on Cyrus.
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