Status & roadmap

IDMX is experimental. Nothing is stable yet, and nothing should carry production mail.

Now: v1-draft-00 in review

The first specification draft, v1-draft-00, is frozen and in public review. Anyone who runs, builds or studies mail systems is invited to comment; the reviewer guide lists the open questions. The review can still change the wire format. Each such change gets a new draft number, so a tagged draft never changes after it is published.

After the review, the spec becomes v1 final. From then on it only gets errata; new behavior goes into a new major version.

Reference implementation

A reference implementation in Rust already covers the whole v1 path: discovery, signing, a receiver and a sender with retries, pinning, a spool queue, SMTP fallback and bounces. A containerized test network runs IDMX-to-IDMX delivery, SMTP fallback and a conformance check against every receiver. See Implementations.

Deliberately not in v1

• Mailing-list semantics (for now, lists send each copy as a new delivery)
• End-to-end encryption and key discovery for it
• Resumable upload for very large messages
• Reports of pinning failures, the IDMX equivalent of TLS-RPT
• Mail client submission and mailbox access (IDMX is server-to-server only)

Later

Once most mail between participating domains flows over IDMX, it can do things that are pointless while SMTP stays an open side door. Examples are first-contact limits for unknown senders and signed sender attestations. They would arrive in a later major version, without changing the basic delivery model.