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Question:

Method GetAttachmentContentID returns empty?

Apr 30 '13 at 10:39

The GetAttachmentContentID is always returning an empty string. All other Methods in attachment concerning methods I have used so far are working fine (getFilename, getContentType, getData…). I need the content ID to replace it within the HTML body with the path to the actual file, to embed the image in the text. Maybe this is the wrong approach for this task using Chilkat?

Answer

I think you might be going about it wrong.

Images that are purely part of an HTML email because they are part of the HTML body composition are not actually attachments. They are "related" items. An HTML IMG tag can reference the image data contained within the email itself in one of two ways -- via a Content-ID, or by Content-Location. I recommend using the Content-Location. See this example:

http://www.example-code.com/ios/smtp_EmbedImage.asp

If you wish to instead use a Content-ID (a "CID" reference in the SRC attribute of the IMG tag), then you would add the related item via the AddRelatedFile or AddRelatedData methods, each of which returns the Content-ID it generated for the related item.

Finally, the fact that GetAttachmentContentID returned an empty string means that the MIME sub-part for that attachment did not have a Content-ID header.

Answer

Here are more details:

PNG:<br> <img src="cid:part1.08060202.00060900@gmx.de" alt=""><br> <br>

with:

pathToDocuments/Attachments/myImage.png

Here an example of a raw email with only the data shortened: 

    +OK
Return-Path: xxxxxxxx@gmx.de
Received: from mout.gmx.net ([212.227.15.15]) by mx-ha.gmx.net (mxgmx009) with
 ESMTP (Nemesis) id 0MIzJh-1UUvSN3KaP-002Tly for xxxxxxxx@gmx.de; Mon, 29
 Apr 2013 17:41:14 +0200
Received: from mailout-de.gmx.net ([10.1.76.27]) by mrigmx.server.lan
 (mrigmx001) with ESMTP (Nemesis) id 0Lflzw-1Upyng1zS6-00pMkn for
 xxxxxxxx@gmx.de; Mon, 29 Apr 2013 17:41:14 +0200
Received: (qmail invoked by alias); 29 Apr 2013 15:41:14 -0000
Received: from unknown (EHLO Admin-Admins-Mac-mini.local) [89.246.74.88]
  by mail.gmx.net (mp027) with SMTP; 29 Apr 2013 17:41:14 +0200
X-Authenticated: #3528779
X-Provags-ID: V01U2FsdGVkX1/WfY5UwVDWyX20EnbsLdIZ7dJ8zTqpez9fdz4CPS
    2iBmqlMoWBlZ75
Message-ID: 517E9499.8090305@gmx.de
Date: Mon, 29 Apr 2013 17:41:13 +0200
From: Peter Falk xxxxxxxx@gmx.de
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:17.0) Gecko/20130328 Thunderbird/17.0.5
MIME-Version: 1.0
To: Andreas Buff xxxxxxxx@gmx.de
Subject: TB: Attachments
Content-Type: multipart/mixed;
 boundary="------------070605040208040605000000"
X-Y-GMX-Trusted: 0
Envelope-To: xxxxxxxx@gmx.de
X-GMX-Antispam: 0 (Mail was not recognized as spam); Detail=V3;
X-GMX-Antivirus: 0 (no virus found)
X-UI-Filterresults: notjunk:1;V01:K0:GBFGcQHllV8=:U1gb2Ir98My3uRl0gRwB7Q
 kZcgU/CXJ4bFHgyj+oFI4X19cOJVaPzg17oeyPHBJdl855ceud3s+WgLyFPvhFrrcMgxnEt
.
.
.
 6PPFpTHS3ghhEUYpL822GWy2E/02yZ4ov+9y9


This is a multi-part message in MIME format.


Content-Type: multipart/alternative;
 boundary="------------020401060503070003040704"


--------------020401060503070003040704
Content-Type: text/plain; charset=ISO-8859-15; format=flowed
Content-Transfer-Encoding: 7bit


PNG:


PDF:


Cheers,
abu


--------------020401060503070003040704
Content-Type: multipart/related;
 boundary="------------090302040100090406030603"


--------------090302040100090406030603
Content-Type: text/html; charset=ISO-8859-15
Content-Transfer-Encoding: 7bit


<html>
  <head>


<meta http-equiv="content-type" content="text/html; charset=ISO-8859-15">



</head>
  <body text="#000000" bgcolor="#FFFFFF">
    PNG:

    

    

    PDF:

    

    

    Cheers,

    abu

  </body>
</html>


--------------090302040100090406030603
Content-Type: image/png;
 name="dehijjjb.png"
Content-Transfer-Encoding: base64
Content-ID: part1.08060202.00060900@gmx.de
Content-Disposition: inline;
 filename="dehijjjb.png"


iVBORw0KGgoAAAANSUhEUgAAAFAAAABQCAYAAACOEfKtAAAahElEQVR42u2ceVBUZ9b/P3Q3
a9PsS7PJJhgQWVwjGBOX6CQRY4hxw9FknEyNmTjECUkmk6kYa7JYM5VY2WYhZUw0iZq4RI2R
.
.
.
5Ens7e3x8fHh3nvvpaWlBZPJhK2tLaWlpRQXF3Po0CHzPU2YMMGsb+C5tFotXV1dREVFUVdX
R2NjI2VlZaSnp7Nu3Tosef6R6H8AULLkbwpX0BEAAAAASUVORK5CYII=
--------------090302040100090406030603--


--------------020401060503070003040704--


--------------070605040208040605000000
Content-Type: application/pdf;
 name="PDF.pdf"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
 filename="PDF.pdf"


JVBERi0xLjMKJcTl8uXrp/Og0MTGCjQgMCBvYmoKPDwgL0xlbmd0aCA1IDAgUiAvRmlsdGVy
IC9GbGF0ZURlY29kZSA+PgpzdHJlYW0KeAEVjD0OgCAUxnZP8Z0AHv+wu7jJ5GwIg4moEL2/
kK5tKyIqhIfQTBORhDEBXigm0TI2XOBrbik/77efaEe3h0EdJYlpF9TIpSXmLKkpFfClCMx3
.
.
.
IDEgMCBSIC9JRCBbIDxlZDMxMjhiZGJmZDFhNmZkZWMwMGU3YTI3YmU2NzU0Yz4KPGVkMzEy
OGJkYmZkMWE2ZmRlYzAwZTdhMjdiZTY3NTRjPiBdID4+CnN0YXJ0eHJlZgoyNDI2NAolJUVP
Rgo=
--------------070605040208040605000000--
.

Answer

If you have a look at the MIME, you can see how it's nested:

multipart/mixed
    multipart/alternative
        text/plain
        multipart/related
            text/html
            image/png
        -- end multipart/related
    -- end multipart/alternative
    application/pdf
-- end multipart/mixed

This is a typical and correct MIME structure. The true attachment is the application/pdf. The "related item" is the image/png. Call GetRelatedContentID instead of GetAttachmentContentID.

Answer

Thank you so much for your fast and useful answers.

I isolated the issue:

GetAttachmentContentID: always returns an empty string, iterating through attachments and iterating through related items.

GetRelatedContentID is working for attachments and for related items.