kumomta/docs/reference/message/parse_mime.md

parse_mime

local mime_part = message:parse_mime()

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

Returns a MimePart representation of the message content.

!!! note While you can modify the returned mime structure, any such changes are not automatically reflected in the message content. You must explicitly re-assign the content via msg:set_data(tostring(mime_part)) to apply them.

Example: attachment extraction

This demonstrates how to obtain a list of all attachments found (recursively) in the incoming message and print out the file name, content type and the decoded content.

This is not a useful production-ready example (you definitely don't want to log all of the attachment content like this!) but can serve as a starting point for policies that need to operate on attachments for scanning, compliance or automation purposes.

kumo.on('smtp_server_message_received', function(message, conn_meta)
  local mime_part = message:parse_mime()
  local structure = mime_part:get_simple_structure()

  for _, attachment in ipairs(structure.attachments) do
    print(attachment.file_name, attachment.content_type, attachment.part.body)
  end
end)