Rust

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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Rust

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

let email = chilkat::Email::new();
email.set_subject("Attachment with a custom header");
email.set_body("The attachment has an extra MIME header.");

// Add an attachment; it becomes attachment index 0.
let _ = email.add_string_attachment("data.txt", "Attachment body.");

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

// The custom header now appears in the attachment's MIME part.
println!("{}", email.get_mime().unwrap_or_default());