Java

Add a Custom Header to an Email Attachment

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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import com.chilkatsoft.chilkat2.Email;

public class ChilkatExample {

    public static void main(String[] args) {
        // Demonstrates the AddAttachmentHeader method, which adds a custom MIME header field to
        // an existing attachment, identified by its zero-based index.

        Email email = new Email();
        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.
        System.out.println(email.getMime());
    }
}