Lua

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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Lua

local chilkat = require("chilkat")

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

local email = chilkat.Email.new()
email.subject = "Attachment with a custom header"
email.body = "The attachment has an extra MIME header."

-- Add an attachment; it becomes attachment index 0.
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.
print(email:get_mime())