Creating sieve script with image attachements

[Phil Pennock]

On 2006-10-24 at 01:54 -0700, Adam D wrote:
> This is the basic script I have been trying to work:
> 
> elsif anyof (header :contains "Content-Type" "gif") {
> fileinto "system.2-mail.missed-spam";
> }

Michael Menge has explained what to look at.  I'll explain why your
approach isn't working.

Where an image is sent as an attachment, rather than as the only content
of the email (and with many mail-clients, even then), the image is one
part of a "multipart" message.

The mail's top-level Content-Type: header will then contain
"multipart/mixed"; each part then has its own set of MIME headers,
including content-type.

You might want to read RFC 2046, section 5.
RFC 2046 is MIME Part 2, Media Types.
Section 5 is "Composite Media Type Values".

What you'll typically see is something vaguely like:

 From: ..
 To: ..
 Subject: foo
 MIME-Version: 1.0
 Content-Type: multipart/mixed; boundary="fred"

 Blurb for non-MIME mail-clients, ignored by all MIME clients
 --fred
 Content-Type: multipart/related; boundary="barney"
 

 --barney
 Content-Type: text/plain; charset=US-ASCII
 Content-Transfer-Encoding: 7bit

 The plain text.

 --barney
 Content-Type: text/html; charset=US-ASCII
 Content-Transfer-Encoding: 7bit

 <p>Some HTML here, with an
  <img src="cid:wilma-gif-2006102400001 at mail.example.org">image inlined</img>
 </p>

 --barney--
 --fred
 Content-Type: image/gif; name="wilma.gif"
 Content-Transfer-Encoding: base64
 Content-Disposition: inline
 Content-ID: <wilma-gif-2006102400001 at mail.example.org>

 base64/text+here==

 --fred--

Or the image might not be flowed inline by the HTML and left as an
attachment which a client might choose to show after the text content.

Regards,
-Phil