parse_mime

local mime_part = message:parse_mime()

Since: Version 2025.10.06-5ec871ab

The functionality described in this section requires version 2025.10.06-5ec871ab of KumoMTA, or a more recent version.

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)