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Question:

Image in Email Handled as Attachment and not Related Data?

Dec 21 '16 at 15:32

I have an email message that contains an embedded image.

The image in the email has a Content-ID and this content ID is referred in the body's html so this should come under the "related data" category, Chilkat handles it as an "attachment".

Why is this the case?

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Answer

A "related item" is an image or other MIME sub-part that is contained within the multipart/related enclosure. I've had a look at the .eml you sent to me in private email, and it has the following MIME structure:

multipart/mixed
    multipart/alternative
        text/plain
        text/html
    image/png

The image is contained in the multipart/mixed enclosure (which is the typical place where attachments are located), and there is no multipart/related enclosure.

For example, a typical email that contains a multipart/related image referenced from HTML, and also has an attachment, would look like this:

multipart/mixed
    multipart/alternative
        text/plain
        multipart/related
            text/html
            image/jpeg
    application/pdf

PS> It's not feasible for Chilkat to be trying to parse the HTML body to determine if a particular image is "related" or not. The decision is based on the location of the image within the MIME structure.

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Answer

Here's another example of an email with incorrect structure, where the HTML images are not properly placed inside a multipart/related enclosure, and are instead located where attachments should be..

multipart/mixed
    multipart/alternative
        text/plain
        text/html
    application/postscript
    application/pdf
    application/postscript
    application/x-zip-compressed
    application/octet-stream
    image/jpeg
    image/jpeg
    image/png
    image/jpeg
    image/png