Add a Custom Header to an Email Attachment

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Demonstrates the Chilkat Email.AddAttachmentHeader method, which adds a custom MIME header field to an existing attachment identified by its zero-based index. This example adds an attachment (which becomes index 0), then attaches an extra header field to it and prints the resulting MIME.

Background: In MIME, every attachment is itself a mini-message with its own small block of headers — things like Content-Type, Content-Disposition, and Content-Transfer-Encoding that describe that specific part. AddAttachmentHeader lets you insert additional fields into that per-part header block, which is occasionally needed for interoperability with systems that look for custom X- headers or content identifiers on individual attachments.

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    //  Demonstrates the AddAttachmentHeader method, which adds a custom MIME header field to
    //  an existing attachment, identified by its zero-based index.

    email := chilkat.NewEmail()
    email.SetSubject("Attachment with a custom header")
    email.SetBody("The attachment has an extra MIME header.")

    //  Add an attachment; it becomes attachment index 0.
    email.AddStringAttachment("data.txt","Attachment body.")

    //  Add a custom header field to the first attachment (index 0).
    email.AddAttachmentHeader(0,"X-Custom-Attachment-Header","some value")

    //  The custom header now appears in the attachment's MIME part.
    fmt.Println(*email.GetMime())

    email.DisposeEmail()