Content-Disposition: inline (was: Re: [Gllug] ADVERT: Free Access to IBM Mainframe running Linux)

[Vidar Hokstad]

On Tue, 2002-10-15 at 17:14, Rev Simon Rumble wrote:
 
> Here's the train of thought:
> 1) Signed messages need a discrete attachment because changes to a
>    single character will cause the signature to be invalidated.
> 2) Since mail clients treat attachments as, well, attachments, there
>    needs to be a way of indicating that this attachment is "message
>    body".
> 3) Outlook Express happily ignores said standard.  Strangely, Outlook
>    works without complaint.

Speaking as someone who's spent a considerable amount of time writing an
e-mail client (a webmail service the company I work for was founded
around), I agree with your interpretation. Anything not marked as
Content-Disposition: inline and not displayable text would be marked
for download, and no other processing would be done.

Marking it with Content-Disposition: inline indicates to me at least
that we would want to do further processing. That processing can be
simple (for pure text, only check for quoted printable or base64
encoding, and deal with charset issues) or it can be hard (html, that
needed significant filtering, especially for a webmail), but ultimately
if we couldn't display it, the fallback would be to offer it for
download to the user just as any other attachment.

Content-Disposition: inline is just a hint. It should never force the
mail client to display something it don't understand - that's just
asking for trouble, because there's so many broken clients out there
that send incredible junk in their outgoing messages.

Brings us back to the Jon Postel quote a few days ago about being
liberal in what you accept and conservative in what you send: If your
mail clients doesn't display a message in a reasonable way, it is 
almost always _your_ client that's at fault, even if the message sent
by someone else was badly broken in the first place :-)

Vidar




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