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rebuild

local rebuilt = mimepart:rebuild()
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.

mimepart:rebuild() will return a new, distinct, mimepart by interpreting mimepart and extracting all of the key features and building up the new mime part from that information.

This is equivalent to the "fix" performed by message:check_fix_conformance except that it does NOT modify the part in-place.

Warning

Rebuilding messages with this method is inherently imperfect: it is based on a deliberately relaxed interpretation of the message content and it is possible, or even likely, that non-conforming input is parsed in a way that results in omitting certain details from the original input.

The purpose of this method is as a best-effort convenience for correcting minor and obviously recognizable issues that cannot easily be resolved at the message generation stage.

It is recommended that you carefully evaluate the effects of this method before deploying it in production.

The example below is purely demonstrative, and it is NOT recommended to be used in production. It is equivalent to the fixing portion of the example found in message:check_fix_conformance, but unconditionally rebuilds every message. It is almost certainly undesirable to run this for any real workload.

kumo.on('smtp_server_message_received', function(msg)
  local mimepart = msg:parse_mime()
  msg:set_data(tostring(mimepart:rebuild()))
end)