Unreleased Changes in The Mainline

Breaking Changes

Enabling batch_handling="BatchByDomain" will cause message:recipient and the recipient field of Log Record to switch to an array holding the list of recipients. These are NOT active by default, but if you wish to enable them you should audit your policy and consider switching to using message:recipient_list as well as review your log processors to ensure that they are able to handle the recipient field being either an array or a string, or otherwise adjusting your log templates accordingly.
HTTP injections no longer consider the Forwarded header as a source of information to populate the received_from metadata. Instead, only the directly connecting IP information will be used. See the upstream issue for more information.

msg:check_fix_conformance now supports optionally detecting and fixing 8-bit charsets.
smtp_server_data event enables once-per-transaction processing of a message and recipient list modification for alias expansion and legal capture.
Admin bounces and scheduled queue suspensions can now optionally target the complete queue name instead of matching by domain/campaign/tenant. This is useful in certain automation scenarios where you wish to target a specific queue precisely. The kcli commands support a --queue option to select the queue name, while the API expose that via a queue_names field.
New kcli xfer and kcli xfer-cancel commands enable migration of queues to alternative kumomta nodes as part of operational tasks such draining a queue for decomissioning or scaling down infrastructure. These commands are building blocks for you to deploy auto-scaling or similar functionality within your infrastructure orchestration. The new xfer_message_received can be used to fixup messages as they are arrive on the target node via xfer. XferOut and XferIn are two new log record types associated with message transfers. The kcli commands have corresponding HTTP API endpoints: xfer and xfer-cancel #311
New kumo.file_type module provides functions for reasoning about file types.
kumo.amqp.build_client is deprecated in favor of kumo.amqp.basic_publish.

smtp server would incorrectly return a 451 instead of a 452 status when max_recipients_per_message or max_messages_per_connection limits were exceeded.