release: 1.4.0: Optional inbound relay (backup-MX) on port 25

Optional inbound relay (backup-MX / forwarder) on port 25, off by default. Mail is accepted only for domains configured in the panel and forwarded to an upstream; there are still no mailboxes. A dedicated security review of the inbound path is still open on the plan (Fable).
Added:
  - `INBOUND_RELAY_ENABLE` (default `false`): when true, Postfix listens on
  - Panel **Inbound** pages (global administrator): domains, upstream host/port
  - Optional `INBOUND_ANTISPAM_MILTER` on the inbound listener only, plus
  - Inbound rate limit (`INBOUND_RATE_LIMIT_MESSAGES_PER_IP`, default 20) and
Changed:
  - Compose publishes host port 25 even when the flag is off (nothing listens
  - Full-backup restore Resync also rebuilds inbound maps when the flag is on.

Full detail: CHANGELOG.md (1.4.0).

docs/roadmap.md

@@ -28,7 +28,6 @@ in `git log` and [CHANGELOG.md](../CHANGELOG.md).
 
 | ID | Topic | Status | Progress | Plan |
 |---|---|---|---|---|
-| inbound-relay | Inbound relay (backup-MX / forwarding) | **agreed** | 0/15 | [plans/inbound-relay.md](plans/inbound-relay.md) |
 | send-log-retention | Send-log retention days in panel Settings | candidate | 0/8 | [plans/send-log-retention.md](plans/send-log-retention.md) |
 | domain-stats-auto-ratelimit | 30-day send stats + auto level-2 rate limit | candidate | 0/11 | [plans/domain-stats-auto-ratelimit.md](plans/domain-stats-auto-ratelimit.md) |
 | contributing | `CONTRIBUTING.md` | candidate | — | — |
@@ -36,12 +35,13 @@ in `git log` and [CHANGELOG.md](../CHANGELOG.md).
 | panel-docs | In-panel operator documentation | candidate | 0/6 | [plans/panel-docs.md](plans/panel-docs.md) |
 | schema-squash | Squash SQLite migrations into a 2.x baseline | **2.x** | — | — |
 
-**Recommended order** (not binding): the next feature is **inbound-relay**.
-**send-log-retention** can land before or beside **domain-stats-auto-ratelimit**
-(panel retention ≥ 30 days helps the stats window). queue-retries shipped in
-[CHANGELOG.md](../CHANGELOG.md) `[1.3.1]`; the 2026-08-13 full-tree review
-follow-ups are in `[1.3.0]`. Candidates need explicit agreement before they
-join the queue.
+**Recommended order** (not binding): the next feature is
+**send-log-retention** once agreed. It can land before or beside
+**domain-stats-auto-ratelimit** (panel retention ≥ 30 days helps the stats
+window). inbound-relay shipped in
+[CHANGELOG.md](../CHANGELOG.md) `[1.4.0]`; queue-retries in `[1.3.1]`; the
+2026-08-13 full-tree review follow-ups are in `[1.3.0]`. Candidates need
+explicit agreement before they join the queue.
 
 After a context reset, pick an item marked `agreed` or `in progress`, then work
 the **Implementation checklist** in its linked plan. The `Progress` column above
@@ -50,27 +50,6 @@ is `done/total` checklist steps in that plan ([development.md](development.md)
 
 ---
 
-## inbound-relay
-
-**Goal:** optional acceptance of mail on port 25 for explicitly configured
-domains, forwarded to an upstream (backup-MX / relay-forwarder). Off by default
-(`INBOUND_RELAY_ENABLE=false`); without the flag the outbound path is
-unchanged.
-
-**Boundary:** an extension of v1.0 — [product.md](product.md) excludes inbound
-mail and mailboxes. This is relay/forward, not IMAP/POP3/webmail; an anti-spam
-engine stays outside the image, only the attachment point is provided.
-
-**Done when:** see the criteria in
-[plans/inbound-relay.md](plans/inbound-relay.md).
-
-**Dependencies / risks:** a finished outbound path; open relay and backscatter;
-a wider attack surface (port 25 accepting mail).
-**Version:** target bump `1.x`; `2.x` possible — to be settled once the
-implementation lands.
-
----
-
 ## send-log-retention
 
 **Goal:** global administrator sets how many days of delivery journal rows