kumomta/docs/reference/kumo.mimepart/new_binary.md

new_binary

kumo.mimepart.new_binary(CONTENT_TYPE, CONTENT, OPTIONAL_ATTACHMENT_OPTIONS)

{{since('2025.10.06-5ec871ab')}}

Constructs a new MimePart for binary content.

You must provide the content type and the content itself; the content can be any binary lua string (including strings that are actually UTF-8 text).

The MimePart will use appropriate transfer encoding for the binary data.

You may optionally specify parameters that will affect how the part will appear when used as an attachment; if you don't care about these, you can omit the third parameter, or pass nil. If you do want to specify them, then you can pass a lua table that allows for the following fields, which influence the Content-Disposition header in the resulting mime part:

• file_name - an optional string to use to define the attachment file name.
• inline - an optional boolean that indicates whether the attachment will be marked as being an inline attachment. The default is false.
• content_id - an optional string that can be used to define the Content-Id header for the mime part, which is useful when generating HTML content that references an attachment.

Example

local kumo = require 'kumo'
local part =
  kumo.mimepart.new_binary('application/octet-stream', '\xbb\xaa', {
    file_name = 'binary.dat',
  })