inbound-antispam-panel: refused inbound mail from mail.log; retention

Step 4/12 of docs/plans/inbound-antispam-panel.md.

The log tailer writes an inbound_spam_log row for mail port 25 refused
(internal/logtail/inbound.go): a "reject:" line of the port-25 smtpd is
Postfix's own policy; a milter-reject / milter-hold / milter-discard
line of cleanup is the filter's verdict. Only a recipient at an inbound
domain is a row, so "Relay access denied" for a stranger's domain is
not. The row is dated by its log line; the reply text is cut to 255
bytes of printable ASCII; a reply starting with 4 is a tempfail.

To tell port 25 from 465 / 587 the listener now logs as
postfix/inbound (syslog_name). cleanup logs under one name for every
listener, so its verdict counts only for a queue id the port-25 smtpd
was seen to open (4096 remembered). Lines are matched from the head,
after timestamp and host: their tail is the sender's own text.

Retention: PruneInboundSpam every six hours - older than the
inbound_spam_log_retention_days setting (seeded from
INBOUND_SPAM_LOG_RETENTION_DAYS, 90, range 7-365), then down to 10 000
rows. The setting has no field in the panel yet.

Known limits, in architecture.md: a log line names one recipient, so a
message refused at end-of-message is one row; a line re-read after an
unclean stop would be a second row.

Checked on the test server, uncommitted tree: go vet ./... ok,
go test ./... ok (22 packages), make e2e ok - the unknown recipient at
the inbound domain refused on port 25 has its row (reject by postfix),
the stranger's domain has none.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/architecture.md

@@ -89,6 +89,19 @@ smtp/inet` removes Debian's stock smtpd). Outbound delivery still uses the
   address is not one - and never refuses anything
   ([internal/milter/inbound.go](../internal/milter/inbound.go)). The headers
   are read only while a filter is attached; refused mail never reaches it.
+  Refusals come from `mail.log`: this listener logs as `postfix/inbound`
+  (`syslog_name`), and the log tailer turns a `reject:` line of
+  `postfix/inbound/smtpd` (Postfix's own policy) and a `milter-reject` /
+  `milter-hold` / `milter-discard` line of `cleanup` (the filter's verdict,
+  counted only for a queue id that listener opened) into a row, dated by the
+  line, when the recipient is at an inbound domain
+  ([internal/logtail/inbound.go](../internal/logtail/inbound.go)). A line
+  names one recipient, so a message refused at end-of-message is one row
+  whatever its recipient count, and a line read twice (the tailer saves its
+  place once a second; an unclean stop can lose that second) is two rows. The
+  journal is pruned every six hours: rows
+  older than the `inbound_spam_log_retention_days` setting, then down to
+  10 000.
   **Inbound relay** (`INBOUND_RELAY_ENABLE=true`): accepts only
   `relay_domains` + `relay_recipient_maps` (`reject_unauth_destination`,
   `reject_unlisted_recipient`). Maps under `/data/postfix/` (`relay_domains`,

docs/guide.md

@@ -209,6 +209,7 @@ expected to set; defaults match the code exactly.
 | `DMARC_MESSAGE_SIZE_LIMIT` | Maximum report message size in bytes when DMARC ingest is on. | `5242880` (5 MiB) | `.env` |
 | `INBOUND_ANTISPAM_MILTER` | Optional milter on the inbound relay listener only (requires `INBOUND_RELAY_ENABLE=true`; not 465/587 or DMARC-only port 25). Empty = off. Format `inet:host:port` or `unix:/path`. Example with [deploy/antispam/docker-compose.antispam.yml](../deploy/antispam/docker-compose.antispam.yml): `inet:antispam:11332`. The panel reads it to report on the *Spam filter* box of the inbound pages and to check that the filter answers (Server › Health). | *(empty)* | `.env` |
 | `INBOUND_ANTISPAM_MILTER_ACTION` | What Postfix does if that milter is down: `accept` (fail-open) or `tempfail` (defer). The *Spam filter* box states which. | `accept` | `.env` |
+| `INBOUND_SPAM_LOG_RETENTION_DAYS` | How long the inbound journal keeps a row, 7-365 days; it also never holds more than 10 000 rows. Seeds the setting on the first start with the inbound relay on. | `90` | `.env` |
 | `INBOUND_JOURNAL_MILTER_SOCKET` | Unix socket of the panel's inbound journal milter, the last milter on port 25 while the inbound relay is on. It records accepted inbound mail and never refuses any; there is no reason to change it. | `/run/selfpost/inbound-journal.sock` | compose |
 | `INBOUND_RATE_LIMIT_MESSAGES_PER_IP` | Coarse per-client-IP cap on inbound smtpd (`smtpd_client_message_rate_limit`). Uses the same window as `RATE_LIMIT_WINDOW_SECONDS`. | `20` | `.env` |
 | `INBOUND_MESSAGE_SIZE_LIMIT` | Maximum message size in bytes on inbound smtpd (`message_size_limit`). When both inbound relay and DMARC ingest are on, the shared listener uses the **greater** of this and `DMARC_MESSAGE_SIZE_LIMIT`. | `26214400` (25 MiB) | `.env` |

docs/plans/inbound-antispam-panel.md

@@ -246,7 +246,7 @@ Target version cut: **`2.1.0`** (MINOR), after `2.0.0`. One commit per step;
 - [x] Agree journal fields, retention, and RBAC (this plan § Decisions) — **Composer**
 - [x] Migration `0002_inbound_spam_log.sql` on the 2.0 baseline — **Composer**
 - [x] Inbound journal-milter + Postfix wiring — **Composer**
-- [ ] mail.log tailer: inbound reject rows — **Composer**
+- [x] mail.log tailer: inbound reject rows — **Composer**
 - [ ] List CRUD + validation + atomic rspamd map sync — **Composer**
 - [ ] Panel: Inbound › Log and Inbound › Filter lists from the kit partials, mockups `in-log` / `in-filter-lists` (add client IP and engine columns mockup-first), evidence pairs — **Composer**
 - [ ] Backup includes `/data/antispam/` — **Composer**

docs/roadmap.md

@@ -30,7 +30,7 @@ in `git log` and [CHANGELOG.md](../CHANGELOG.md).
 |---|---|---|---|---|
 | preflight | Installation check page (`/preflight`) | candidate | — | [plans/preflight.md](plans/preflight.md) |
 | contributing | `CONTRIBUTING.md` | candidate | — | — |
-| inbound-antispam-panel | Inbound antispam journal + allow/deny lists | in progress | 3/12 | [plans/inbound-antispam-panel.md](plans/inbound-antispam-panel.md) |
+| inbound-antispam-panel | Inbound antispam journal + allow/deny lists | in progress | 4/12 | [plans/inbound-antispam-panel.md](plans/inbound-antispam-panel.md) |
 | inbound-quarantine | Inbound spam quarantine (hold / review / release) | candidate | — | [plans/inbound-quarantine.md](plans/inbound-quarantine.md) |
 | csrf-tokens | Per-session CSRF tokens on state-changing forms | candidate | — | — |
 | template-data-typing | Typed structs for template data instead of `map[string]any` | candidate | — | — |