This project is not a UI for the kumomta but cover some functionality like.
Inbound/Outbound routing (based on email or domain with ability to act as smart host or sending the incoming mails to a webhook )
Bounce processing with automatic suppression
DKIM generation and signing
ACME Certificate issuing
Feedback Loop processing
Mail log retention
DMARC parsing and reporting
Project is completely open source and you can find it here Iris