Case in Email Headers

[Chris Croome <chris@xxxxxxxxxxxxxxxxxxx>]

Hi

I have been talking about this with the guy I work with who runs our
mail servers and basically mail servers take no notice whatsoever of
headers and just use the email envelope for delivering mail.

The things that might break with all lower case headers are things
like people procmail scripts that look for a case sensitive match.

For example, this rule I have to put mail from this list into a
seperate mbox file:

  # ietf-message-xml
  :0:
  * ^List-ID:.*<ietf-message-xml.imc.org>
  lists.ietf-message-xml

Would break if the list-id header was lower case.

Following is something he has written about this.

Chris

----- Forwarded message from Bruno Postle <bruno@xxxxxxxxxxxxxxxxxxx> -----

Date: Tue, 11 Feb 2003 11:02:03 +0000
From: Bruno Postle <bruno@xxxxxxxxxxxxxxxxxxx>
To: Chris Croome <chris@xxxxxxxxxxxxxxxxxxx>
Subject: Re: Fwd: [chris@xxxxxxxxxxxxxxxxxxx: Re: XML message format draft]

On Mon 10-Feb-2003 at 01:09:58PM +0000, Chris Croome wrote:
> 
> Can you let me have some examples of case conventions in email headers
> that the two Perl modules linked to in the attached email don't cover.

This is the rfc: http://www.faqs.org/rfcs/rfc2822.html

2.2. Header Fields

   Header fields are lines composed of a field name, followed by a colon
   (":"), followed by a field body, and terminated by CRLF.  A field
   name MUST be composed of printable US-ASCII characters (i.e.,
   characters that have values between 33 and 126, inclusive), except
   colon.  A field body may be composed of any US-ASCII characters,
   except for CR and LF.  However, a field body may contain CRLF when
   used in header "folding" and  "unfolding" as described in section
   2.2.3.  All field bodies MUST conform to the syntax described in
   sections 3 and 4 of this standard.

The convention is to capitalise each word like this:

    Content-Transfer-Encoding: 7bit

..but there two common exceptions:

    MIME-Version: 1.0
    Message-ID: <20030211103735.GB18894@xxxxxxxxxxxxxxxxxxx>

..however the mutt developers do them like this:

    Mime-Version: 1.0
    Message-ID: <20030211103735.GB18894@xxxxxxxxxxxxxxxxxxx>

All the other mixed-up-case headers are always 'X' headers, and so
unimportant:

exchange:

    X-MSMail-Priority: Normal
    X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1106

gnu-mailman:

    X-BeenThere: sheffcol-web@xxxxxxxxxxxxx

croome:

    X-PGP-Key: http://chris.croome.net/pgp.html
    X-PGP-KeyID: 0x8BB2DE91

-- 
Bruno

----- End forwarded message -----

-- 
Chris Croome                               <chris@xxxxxxxxxxxxxxxxxxx>
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