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Rewrite as a Rust, Apache-2.0 workspace

Browse Source 
Supersedes the Go + embed-Mox design. The Go tree is removed; its
architecture doc is preserved at docs/archive/ARCHITECTURE-go-embed-mox.md
because its competitive analysis and data model still hold.

Five decisions recorded as ADRs:

  0001  Rust, not Go — accepting ~5,500 lines of protocol code that Mox
        would have given us free, to get the first permissively licensed
        Rust mail server. Costs stated plainly.
  0002  Apache-2.0, not MIT or AGPL — patent grant, trademark, CLA-free
        contribution. Public on GitHub; Gitea stays as the private fallback.
  0003  Stalwart's primitive crates (Apache-2.0/MIT) yes; its AGPL server
        crates never. DANE and MTA-STS sit on the AGPL side of that line,
        which is why we write our own.
  0004  Milestones, reordered: embedded inbound is required at launch.
  0005  Oracle Cloud blocks outbound :25, so direct-to-MX is impossible on
        the launch host. Split delivery is mandatory, not an on-ramp.

Twelve crates in three tiers. Tier 1 (mail-dane, mail-mta-sts, mail-dsn)
is standalone and publishable — no `dane` or `mta-sts` crate exists on
crates.io at all today.

openmail-relay ships the provider table as data, with SES and Oracle from
the start. Oracle's and Resend's SPF includes are deliberately None: a
guessed include turns the DNS check green against a mechanism the provider
does not honour, and mail still fails SPF silently.

cargo check/test/clippy/fmt all green; unsafe_code is forbidden workspace
wide; cargo-deny enforces the licence policy in CI.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JkyvfNJGTshJNE9FtwPLk7
This commit is contained in:
Karti Tripathi
2026-09-02 13:08:05 -07:00
co-authored by Claude Opus 5
parent 428040d964
commit 36b15ddcaf
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docs/adr/0005-oracle-cloud.md
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# ADR 0005 — Oracle Cloud as the launch host, and what it forbids
**Status:** Accepted, 2026-09-02.
## The constraint
**OCI blocks outbound TCP/25 for every tenancy created after 2021-06-23.**
Exemption is a service-limit request, routinely refused for free tier. Inbound
:25 is *not* blocked.
| | On OCI |
|---|---|
| Receive on :25 | ✅ works — `openmail-smtpd` is fine |
| Relay out on 587 | ✅ works (verify: see below) |
| Direct-to-MX | ❌ **impossible.** `mail-dane` and `mail-mta-sts` can never run there |
## Decision
Launch on OCI in **split delivery**: receive directly, relay outbound. Support
Oracle Cloud Email Delivery *and* SES as relay providers from day one — two
providers at launch forces the provider abstraction to be genuinely
data-driven instead of an SES-shaped `if`.
Direct-to-MX (v0.4) is developed and tested on a host without the block.
## Consequences
- Embedded inbound moves from "milestone 4, later" to **required at launch**.
- The relay path is not a temporary on-ramp; on our own launch host it is the
only outbound path that exists.
- Oracle's SPF include is region-scoped (`rp` / `eu.rp` / `ap.rp`
`.oracleemaildelivery.com`), so `providers.rs` deliberately stores `None` and
makes the operator paste theirs. A guessed include turns the DNS check green
against a mechanism the provider does not honour and mail still fails SPF —
silently. Same for Resend.
## ⚠️ Open — verify before committing to the host
Oracle's docs name only port 25. Mailcow community reports claim **587 and 2525
are also blocked outbound on free tier**, which would make OCI unable to relay
either, and would change the host choice entirely.
**Test on a free instance before building on this.** It is a 20-minute check
and it invalidates this ADR if the reports are right.