OT: Mail system trashes Swedish flag

[Tim]

Allegedly, on or about 20 March 2013, Jonathan Ryshpan sent:
> I'm a little perplexed.  Linux doesn't mark files with their type, as
> Mac systems do.  The file has a .pdf extension, and the file command
> shows it as PDF type.
>         $ file SwedishFlag.pdf 
>         SwedishFlag.pdf: PDF document, version 1.5

When you attach a file to an email, the mail headers identify the type
of file that's being attached, to *help* the recipient handle it (it
particularly helps in the cases where it's useful to know what the file
is before it's un-encoded from the message).  This is an email issue,
not an OS issue.

On the whole, Linux identifies types of files by examining their
content.  Applications can ask the system to identify the file for them,
then use that information.  Applications could also use another
technique.  For example, the Apache webserver does use the filename
suffixes as a filetype identifier.

> > How did you email it?  What mail program did you use?

> The email program is evolution.  I clicked "Send".

I'm using Evolution, too.  I should probably have asked those questions
a bit better.  I was thinking along the lines of was it "attached" or
just dumped into a message editor.  Or, a mail program (like Evolution)
or a webmail service.  But you've answered that, by now.

> Here is the start of the section of the message containing the
> attachment in question:
>         Content-Type: application/pdf; name="SwedishFlag.pdf"
>         Content-Description: 
>         Content-Disposition: inline; filename="SwedishFlag.pdf"
>         Content-Transfer-Encoding: 8bit

That looks normal.  However, some seriously out-of-date clients might
expect older descriptions, and be looking for something else.  That's
their problem, though, not yours.

e.g. "application/x-pdf"

> I've attached a copy of SwedishFlag.pdf.  Also SwedishFlag.zip, as
> suggested in an earlier posting.  Let's see what the mail system does to
> them in Linux systems.

I received the PDF with appropriate headers, and it's viewable in the
PDF viewer.  Likewise with the ZIP file, and the PDF inside it.

Interestingly, the PDF file is sent as 8-bit.  It's sent "as-is" and not
further encoded.  But the ZIP file has been base64 encoded.  I suppose
there is the chance that your recipient has received the mail through
one of those broken services which (allegedly) "helpfully" transcode
8-bit data on the way through them, and mangle it in the process.
Again, that would be something out of your control, and not your
problem.

I'd ask your problem recipient to send one your mails back to you, with
all its attachments intact.  e.g. Forward your message as an attachment
to one of theirs.  Then you can have a look at the message source, to
see if they've received it in the same manner that you sent it.

I don't think you mentioned what the recipient was using.  Linux,
something else?  Would they know what they're doing, would they expect
the computer to do everything for them automatically?

-- 
[tim at localhost ~]$ uname -rsvp
Linux 3.7.9-104.fc17.x86_64 #1 SMP Sun Feb 24 19:19:12 UTC 2013 x86_64

All mail to my mailbox is automatically deleted, there is no point
trying to privately email me, I will only read messages posted to the
public lists.

My apologies for not including a virus with this message, but I don't
use Windows.