selfpost/CHANGELOG.md

# Changelog

All notable changes to this project are documented here.
Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/); versioning follows [SemVer](https://semver.org/).

## [Unreleased]

### Fixed

- A bounce could be recorded as a successful delivery. The log-tailer's
  delivery-line pattern matched `status=` greedily, so it took the *last*
  occurrence on the line — and Postfix appends the remote server's reply
  verbatim, which the far end controls. A rejection whose reply text contained
  `status=sent` was filed as `sent` in the send log. The pattern now takes the
  first `status=` after the recipient, which is the real field
  (`internal/logtail/logtail.go`); found while extending `TestParseDelivery`.
- Log-tailer resumes where it stopped instead of jumping to end-of-file on
  every start (phase 3, `docs/code-review.md`): the read position and a
  fingerprint of the log's head are persisted (`logtail_state`, migration
  `0003`), so delivery lines written while the panel was down are parsed and
  their send-log rows no longer stay `queued` forever. A log that changed
  identity while the panel was down is read from the start; a first-ever start,
  with nothing stored, still begins at the end. Container recreate remains a
  gap — `mail.log` is not in `/data` (`docs/security.md`).
- Level-2 rate limit no longer overshoots under concurrency: messages that
  passed the check at MAIL FROM but have not reached the send log yet are
  counted alongside the stored rows (`internal/milter/inflight.go`), so
  parallel SMTP sessions cannot each spend the same last slot. Slots are
  released at end-of-message, on ABORT, and after a 10-minute TTL, so a client
  that drops mid-transaction cannot hold one — the limiter stays fail-open.

### Changed

- The project has a single public home: `github.com/mixeme/selfpost`. Codeberg
  is being retired, so the Go module path moved with it — `go.mod`,
  `test/e2e/go.mod`, every import, the `Makefile` `MODULE` variable and the
  `-ldflags` version stamp in `build/Dockerfile` and `docs/development.md`. An
  import path pointing at a host that is going away would break `go get` and
  `go install` outright, which is why this is not only a documentation change.
  README no longer lists a primary/mirror pair.
- Code comments no longer cite the archived specification. References like
  "spec 7.6.1" or "spec 5.1" pointed into `docs/archive/specification-v1.0.md`,
  which is explicitly not a source of truth; each is now a reference to the
  live document that owns the subject — `docs/architecture.md` (with section),
  `docs/product.md`, `docs/security.md`, or the README. Comments only; no
  behaviour is affected.
- `docs/architecture.md` gained a *Code layers* section: a diagram of
  handlers → services → store plus the adapters, and the reason the services
  layer exists (multi-store writes and their rollback) — closing item A2 of
  `docs/code-review.md`.
- Phase 1 doc/code hygiene (`docs/code-review.md`): removed ~30 stale
  "Phase N" / historical-staging references from code and shell-script
  comments (`cmd/panel`, `internal/*`, `build/*`) now that v1.0 is done;
  fixed a stale dashboard comment (`internal/web/handlers_domains.go`)
  claiming applications/send-log were unimplemented; added a CSRF ADR to
  `docs/security.md` (why Origin-check, not tokens); resolved `docs/logo` in
  `docs/roadmap.md` (directory doesn't exist, criterion already met); added a
  `gofmt -l` check to CI (`.github/workflows/test.yml`).
- Phase 2 GUI polish (`docs/code-review.md`): the monitoring pages stop
  polling while their tab is hidden — the skip is done in an
  `htmx:beforeRequest` listener (`internal/web/static/panel.js`) rather than
  htmx's own trigger filter, which is evaluated with `new Function` and would
  be blocked by the panel's CSP. Dark mode is now a single reassignment of CSS
  custom properties under `prefers-color-scheme: dark` instead of a cascade of
  `!important` overrides, and the duplicate `main { max-width }` rule is
  consolidated into one base rule with documented per-page overrides
  (`internal/web/static/panel.css`).

### Security

- Pre-release security review (plan § D, model Fable, 2026-08-06): full pass
  over the diff from the v1.0 audit (Phase 11, `bd64e80`) to HEAD plus the
  complete spec 7.6 checklist. No exploitable findings; one defence-in-depth
  fix below. Accepted risks in `docs/security.md` unchanged.
- `saslpasswd2` argv: the application login is now passed after a `--`
  end-of-options marker (`internal/app/sasl.go`), so a login starting with
  `-` (legal under the whitelist) can never be parsed as a flag by getopt.

### Added

- Optional password encryption for the two secret-bearing downloads (plan
  phase 1.5, `docs/code-review.md`): an *Encrypt with a password* checkbox on
  the full-backup and domain-export forms writes a `.spbk` / `.spde` envelope
  instead of the plain `.tar.gz` / `.json` — scrypt key derivation and
  AES-256-GCM over 64 KiB chunks, each authenticated with the header, its
  counter and an end-of-stream flag, so a truncated or altered file refuses to
  open (`internal/secretfile`). Unticked, both downloads are byte-for-byte what
  they were.
- Domain import accepts an encrypted export: the envelope is detected by its
  magic bytes, and a password field appears next to the file picker
  (`internal/web/handlers_backup.go`, `templates/encrypt_fields.html`).
- `selfpost-backup` writes encrypted archives and reads them back:
  `-decrypt` (with `-i`/`-o`) turns a `.spbk` into the plain `.tar.gz` a
  restore unpacks. The password comes from `SELFPOST_BACKUP_PASSWORD` or
  `-password-file`, never from argv.
- `TestParseDelivery` covers the exotic mail.log shapes the review asked for
  (`docs/code-review.md` § 3): a `status=` quoted inside the remote reply, the
  null recipient of a double bounce, `orig_to=` alongside `to=`, an
  unrecognised status word, a capitalised one, and a cleanup line.
- docs: README *Encrypting a backup or export*; `docs/security.md` §
  *Резервная копия и экспорт домена* + accepted risk (encryption is opt-in);
  `docs/architecture.md` persistence § envelope summary.
- docs: `docs/roadmap.md` v1.x tail — retire `implementation-plan.md` in the
  release commit (move to `docs/archive/`, retarget its references in README,
  docs, Makefile, release workflow and the e2e test comment).
- docs: `docs/code-review.md` — phase 1.5 plan for optional password encryption
  of full backup (`.spbk`) and domain export (`.spde`); checkbox UI pattern;
  remove session-resurrection-from-backup as accepted risk.
- docs: `docs/code-review.md` — full codebase review (architecture, code quality,
  documentation, GUI, legacy, risks) with prioritized implementation plan and
  model routing; cross-links in `implementation-plan.md` and `progress.md`.
- docs (D6): Docker `HEALTHCHECK` probes `/healthz`; endpoint returns 503 unless
  opendkim, panel, and postfix are RUNNING (`internal/health.Liveness`).
- docs (D6): README *Container health* — scope of `/healthz` vs authenticated Status.
- docs (D7): `cmd/panel/envdoc_test.go` — regression test that every
  `loadConfig` and build-script env key is listed in README documentation.
- docs (D8): `docs/architecture.md` — as-built processes, mail path, routes,
  persistence (verified against code).
- docs (D8): `docs/development.md` — local Go workflow, `make e2e`, dev-server
  loop, commit/CHANGELOG protocol, agent rules.
- docs (D9): `docs/product.md` — product purpose, assumptions, out-of-scope,
  multi-domain model.
- docs (D9): `docs/security.md` — self-contained mandatory security checklist
  (former spec §7.6).
- docs (D9): `specification.md` archived to
  `docs/archive/specification-v1.0.md`; live docs updated (`progress.md`,
  `implementation-plan.md`, `roadmap.md`, `documentation-plan.md`).
- docs (D1): README *Operations* — panel screens (`/status`, domains,
  deliveries, mail queue, system log, backup, account), upgrade procedure,
  session behaviour (sliding idle, monitoring polls do not extend, password
  change signs out other sessions), and `mail.log` rotation cadence.
- docs (D1): README *Rate limiting* — level-1 anvil limits
  (`RATE_LIMIT_MESSAGES_PER_IP`, `RATE_LIMIT_WINDOW_SECONDS`) and level-2
  per-domain/application limits from the panel; fixes the `.env.example` link
  that pointed at a missing section.
- docs (D2): README environment-variable reference — public `.env` table with
  code-accurate defaults, `TRUSTED_PROXY_CIDR` security note, explicit
  internal-variable list; `TRUSTED_PROXY_CIDR` wired through
  `deploy/docker-compose.yml`.

### Removed

- docs: `security.md` — accepted risk «restore old backup revives session rows»
  (not a concern in operator deployment).

### Changed

- docs: `implementation-plan.md` trimmed to the sole open v1.x gate — pre-release
  security review (§ D); closed B.1–C.4 material moved to as-built and ops docs.
- docs: `architecture.md` — sessions (SQLite, idle renew, password change),
  `mail.log` rotation (rename + `postfix reload`), `SELFPOST_HOSTNAME` startup
  gate, log-tailer known gaps.
- docs: `development.md` — expanded e2e stack and `release.yml` matrix workflow.
- docs: `security.md` — accepted risk for send-log rows stuck at `queued` after
  panel restart or container recreate.
- docs: `roadmap.md` — optional send-log / `mail.log` follow-ups under v1.x tail.
- docs: `progress.md`, `documentation-plan.md` — cross-links updated for the new layout.
- docs: `documentation-plan.md` marked closed (D1–D9); trimmed to package
  checklist, code-verification method, and ongoing maintenance rules.
- docs: `roadmap.md` — v1.x doc/deploy tail (Codeberg Quick start, compose
  image tag at release, `docs/logo`); archived-spec references replaced with
  `product.md` / `security.md` / `development.md`.
- docs: `progress.md` — documentation pass closed; deferred polish in roadmap.
- `/healthz` now checks supervisord mail-path processes, not HTTP alone.
- `build/Dockerfile`: `curl` for `HEALTHCHECK`; probe on port 8080.
- docs (D3): README backup — stopped-container `tar` of `./data` (with live-container
  WAL warning), `manifest.json` consumed after a matching restore.
- docs (D4): README status banner (v1.0 implemented, links to open questions and
  documentation pass); new *Published ports* note for 587; compose usage comment
  corrected (TLS via `./certs` bind mount, not `.env`).
- docs (D5): `implementation-plan.md` B.1 — password change signs out other
  sessions only (implementation diverged from original plan; README was already
  correct).
- docs: documentation plan now targets retiring `specification.md` after D9 —
  migration map to `product.md`, `architecture.md`, `development.md`, and
  expanded `security.md`; D9 added to the release gate.

## [0.4.0] - 2026-08-04

### Added

- The project's mark is now in use rather than only on file. The README opens
  with the full stamp; the panel carries the compact one at the left of its
  navigation bar, linking to the status page, and the full one above the card
  on the two pages that have no navigation — sign-in and first-run setup. The
  browser tab icon changes with it, from the earlier envelope drawing to the
  stamp's small-size variant, so the tab, the panel and the README are one
  identity. The four brand files in `docs/assets/` had their wordmark converted
  from live text to outlines: they were set in IBM Plex Sans, which is not
  installed on the machines that render them, and the light/semibold contrast
  between *Self* and *Post* — the whole of the mark — collapsed into whatever
  fallback the viewer happened to have.

### Changed

- panel: the sign-in and setup pages are now a column the width of their own
  card. Both are a single narrow card, which centred itself while the heading
  above it stayed at the panel's left edge; adding the mark would have made
  that three alignments on a page with four elements.

- panel: the three monitoring pages — Deliveries, Mail queue, System log — are
  now laid out wider (64rem against the 48rem the rest of the panel keeps).
  They carry data rather than prose: the send-log's seven columns had no room
  to breathe, and the raw `mail.log` lines wrapped every second line.

### Fixed

- panel: Deliveries now shows the subject as text rather than as its MIME
  encoding. A subject in any non-Latin alphabet reaches the milter as RFC 2047
  encoded-words (`=?utf-8?Q?=D0=9F…?=`), and the panel printed that verbatim —
  unreadable, and as one unbreakable run wide enough to push the Status column
  outside the card. Subjects are decoded when the message is journalled and
  capped at 200 characters; the column clips anything still too long to one
  line, with the full text in the tooltip. Rows logged before this release keep
  their raw string. Subjects in the legacy single-byte charsets (windows-1251,
  koi8-r) are still stored as sent — there is no decoder for them.

- panel: table cells may now break inside a word, so no single long value can
  push a table past the edge of its card. A 40-character recipient address did
  it just as readily as an undecoded subject: a column is at least as wide as
  the longest unbreakable run it holds, and email addresses have nothing to
  break on. Timestamps are exempt and stay on one line.

- panel: the Applications list on a domain page no longer comes apart. It was a
  four-column table whose last column held six controls, two of them expanding
  panels with textareas — far more than the width of a column, so the controls
  broke into a staircase, the login cell grew into a block as tall as the row,
  and the two text columns were left stranded on the baseline halfway down it.
  An application is now a block rather than a row: the login on one line, mode
  and addresses on the next, and the controls in a single wrapping row, with an
  opened panel claiming the full width for its fields.

## [0.3.0] - 2026-08-03

### Fixed

- panel: the PTR (reverse DNS) check no longer reports a correctly published
  record as wrong. The checks went through the container's own resolver, which
  forwards to the host's systemd-resolved — and systemd-resolved answers the
  reverse lookup of the machine's own IP from the local hostname instead of
  asking public DNS. A server with `203.0.113.10 → selfpost.example.com` in DNS
  was told its PTR pointed at the provider-assigned hostname. All four
  deliverability checks (PTR, SPF, DKIM, DMARC) now query recursive resolvers
  directly, so the panel reports what a receiving mail server actually sees.
  Set `SELFPOST_DNS_RESOLVERS` if outbound port 53 is closed or you run your
  own recursor; it defaults to 1.1.1.1, 8.8.8.8 and 9.9.9.9.

### Changed

- panel: the three monitoring pages now live at URLs that match their nav
  labels — Deliveries at `/deliveries` (was `/sendlog`), Mail queue at
  `/mail-queue` (was `/queue`), System log at `/system-log` (was `/logtail`).
  Bookmarks to the old paths stop working.

- panel: each entry in the navigation bar now carries an icon beside its label,
  so the bar is scannable at a glance instead of a row of similar-length words.
  The icons are inline SVG drawn in the entry's own colour — no extra request,
  no exemption from the panel's Content-Security-Policy — and are hidden from
  screen readers, which still announce the label alone.

- panel: the navigation bar is laid out as two rows on purpose — the signed-in
  user, Account and Sign out along the top right, the page entries below. It no
  longer fits on one line and used to wrap on its own, which left the session
  block sitting left-aligned under the entries as if it were more navigation.

## [0.2.0] - 2026-08-03

- panel: every authenticated page now ends with the running version
  (`SelfPost 0.2.0`) in a small footer. It is the value a backup manifest is
  checked against on restore, and the first thing to establish when the panel
  behaves unexpectedly. The login and setup pages deliberately do not show it.

- panel: the domain page now shows the **SPF and DMARC records it expects**,
  with host, value and a Copy button, next to the DKIM record it already
  showed — previously it only said "also configure SPF and DMARC (see the
  documentation)" and the concrete example appeared only once a check had
  already failed. The SPF value names the addresses this server's hostname
  resolves to (falling back to an `a:` mechanism if it does not resolve), and
  the DNS checks below build their remediation advice from the same source, so
  the page and its checks cannot recommend different records.
- panel: one appearance for actions. Several controls — a POST wrapped in an
  inline form (Re-check, Export domain, Sign out, New password…), the
  `<details>` toggles in the applications table, the delete links — used to
  render as bold blue text while everything else was a button, so the same
  kind of control looked like two different things, sometimes within one card.
  They are all buttons now: filled for a card's own action, compact and
  outlined where actions cluster in a table row or the nav bar. The two
  actions that are really navigations — "Delete domain" and the status page's
  "Full queue" — are anchors carrying the same button styling. A bare link is
  left only where it reads as part of a sentence, a table cell or the nav.
- panel: on the domain page **Add an application** now sits directly above the
  **Applications** list — the same order the domains page uses for its own add
  form — instead of being stranded below the domain rate limit.
- ci: hermetic container e2e suite (`test/e2e`, a separate Go module) gates
  image publishing — `make e2e` locally, and `go test ./...` in `test/e2e` as
  a required step in `release.yml` before a version tag's image is pushed.
  It builds the real image, brings up the shipped `deploy/docker-compose.yml`
  plus a test-only override (self-signed cert, low ports, a fake DNS zone
  served by CoreDNS, a `smtp-sink` sink-MX) on an isolated compose project,
  then drives the panel over HTTP exactly like an administrator: setup →
  login → add a domain → publish the DKIM record it prints into the fake zone
  → add an application → send over SMTP AUTH → verify the delivered message's
  DKIM signature against the record the panel published → poll the send log
  to `sent`. Negative coverage: no-AUTH and unauthenticated-relay rejection,
  sender/login mismatch, the level-1 (anvil) and level-2 (panel-configured)
  rate limits, the journal-milter's fail-open behaviour when the panel process
  is stopped, a missing/malformed `SELFPOST_HOSTNAME` failing the container
  fast, and a login session surviving `docker restart`. `release.yml` moved
  off qemu to a native per-architecture build (`ubuntu-latest` /
  `ubuntu-24.04-arm`), each gated by this suite before its tag is pushed and
  merged into the version manifest — running the full Postfix/OpenDKIM stack
  under emulation for the gate was impractically slow.
- ops: `mail.log` rotation switched from `copytruncate` to rename +
  `postfix reload` (the same mechanism `postfix logrotate` itself uses),
  eliminating the up-to-one-second window in which `copytruncate` could drop
  in-flight delivery lines — a lost line meant a send-log row stuck at
  `queued` forever. `logrotate-mail.conf` keeps `create 0644 root root`
  rather than `nocreate`: verified on a live container that letting Postfix
  recreate the file itself on reload produces `0600`, which the unprivileged
  panel process cannot read, breaking the mail-log view until the next
  restart. The panel's log-tailer (`internal/logtail`) re-drains the old file
  descriptor once more right before switching to the rotated one, closing a
  similar small window between polls; a missing `mail.log` right after
  rotation is now a normal empty screen rather than a logged error.
- panel: login sessions now persist in SQLite instead of memory, so an
  administrator's login survives a container restart or redeploy. Only the
  SHA-256 of the session token is stored, never the token itself. The
  absolute 12-hour TTL is replaced by a **sliding idle timeout**
  (`PANEL_SESSION_IDLE_DAYS`, default 7 days, no absolute cap): the
  monitoring screens' background polling does not count as activity, so a
  forgotten open tab does not keep a session alive forever. Changing the
  password still signs out every other session.
- panel: security headers on every response — `Content-Security-Policy`,
  `X-Content-Type-Options`, `X-Frame-Options`, `Referrer-Policy`, and
  `Strict-Transport-Security` where the deployment is HTTPS-only. They are
  emitted by the panel itself, so the reverse proxy still needs no security
  configuration of its own.
- panel: state-changing requests are now checked against the panel's own
  origin (`Sec-Fetch-Site`, falling back to `Origin` vs `Host`). This closes
  cross-site request forgery from a *neighbouring host on the same domain* —
  a CMS or a forgotten staging subdomain next to the panel — which the session
  cookie's `SameSite=Lax` counts as same-site and therefore cannot stop. A
  request that sends neither header is still let through, so genuinely ancient
  browsers keep working. **The reverse proxy must pass the original `Host`
  header through** (every shipped fragment already does); one that rewrites it
  makes the panel refuse every form submission, and the log line names both
  the `Origin` and the `Host` it compared.
- panel: the session cookie is now named `__Host-selfpost_session` wherever it
  is `Secure` (the standard deployment), which makes the browser enforce that
  no other host can set or overwrite it. **Upgrading signs the administrator
  out once.** With `PANEL_COOKIE_SECURE=false` the old name is kept, because
  the prefix is invalid without TLS. Signing out clears both names.
- panel: if a request arrives with two cookies of the session cookie's name —
  what a neighbouring host does when it overwrites the session — the request
  counts as signed out and the log says so, instead of the panel silently
  picking the other host's value and looping back to the login form forever.
- panel: the layout's stylesheet moved to `/static/panel.css` and the
  confirmation prompts on destructive buttons moved into `/static/panel.js`.
  No visible change; the panel's CSP allows no inline script or style, and
  this is what keeps that policy free of exemptions.
- docs: the first-run setup link is also written to `/data/setup-token`
  (`0600`) — documented in the README as the way to read it without the token
  passing through a container-log pipeline.
- panel: new **Status** page — supervised processes, mail queue, TLS
  certificate expiry, milter sockets and the server's own hostname/reverse-DNS
  (FCrDNS) check — and it is now the panel's landing page. The local checks
  refresh by polling; the DNS lookup is cached with a *Re-check* button.
- panel: the domain page shows a **DNS status** card: the published DKIM record
  compared against the key this server actually signs with, plus SPF and DMARC.
  The SPF check is deliberately shallow — it looks for a mechanism literally
  covering this server's address and does not follow `include:`/`redirect=`, so
  a record that authorises the server through an include is reported as "cannot
  tell", not as a failure.
- panel: the domain list moved from `/` to `/domains`; `/` redirects to the
  status page. The **Reload** button moved from the domain list to the status
  page and now explains what it regenerates and when to use it.
- fix: the panel could never read the mail queue in the documented deployment.
  `postqueue` relies on its setgid-`postdrop` bit, which `no-new-privileges`
  (set in the shipped compose file) disables, so the *Queue* screen always said
  "Could not read the mail queue". The `panel` user is now a real member of
  `postdrop`.
- panel: navigation bar is now rendered once from the shared layout, so every
  authenticated page has it — including the domain page and the delete
  confirmation, which had no navigation links at all — and the current page is
  highlighted instead of silently missing from the list.
- panel: new *Account* page to change the administrator's username and/or
  password (the current password is required, throttled on the same limiter as
  the login form). Changing the password invalidates all other sessions.
- panel: *Backup & migration* moved off the domain list onto its own *Backup*
  page, with the full backup and the domain import as two separate cards.
- panel: the domain page now shows the *Sending server settings* (server,
  port and encryption) needed to configure a mail client; port 587 is listed
  only when `SUBMISSION_ENABLE=true` for this deployment.
- panel: *Copy* buttons on the DKIM record, on a newly issued application
  login/password and on the sending server name.
- panel: the *Addresses* field is hidden while an application's address mode is
  *Any address of the domain*, where the server ignores it.
- ci: disable provenance attestation on release image push, so the ghcr.io
  manifest list shows only `linux/amd64`/`linux/arm64` (no `unknown/unknown`).
- ci: run `go vet` and `go test ./...` on every push to `main` and every pull
  request, not only the image build on a release tag.
- security: optionally honour `X-Forwarded-For` for login/setup rate-limiting
  when the request's direct peer is in the new `TRUSTED_PROXY_CIDR` list,
  giving real per-client limits behind a reverse proxy instead of one global
  bucket. Unset by default (unchanged `RemoteAddr`-only behaviour).

## [0.1.0] - 2026-07-15

Initial feature-complete implementation of the v1.0 specification (phases 0-11
of `docs/implementation-plan.md`).

### Added

- Panel (Go, single static binary) with SQLite persistence, one-time
  crypto-random setup link, bcrypt admin auth, session cookies.
- Domain management with per-domain DKIM (RSA-2048, generated in pure Go) and
  OpenDKIM KeyTable/SigningTable regeneration + privilege-safe reload.
- Application (sender identity) management: SASL credentials via `sasldb2`,
  `smtpd_sender_login_maps` enforcing sender/domain ownership, no open relay.
- Full Postfix relay config generated from env at container start: SMTPS 465,
  optional STARTTLS submission 587, SASL auth, TLS for outbound delivery,
  anvil-based rate limiting (level 1).
- Journal milter (pure Go, `go-milter`) recording every send to `send_log`;
  fail-open by design so a milter fault never blocks mail.
- Monitoring UI: send log, Postfix queue, and mail.log tail, all
  HTMX-polling, HTML-escaped.
- Per-domain/per-application sending rate limit (level 2), enforced in the
  journal milter at `MAIL FROM`, fail-open on the limiter's own errors.
- Full backup/restore (`tar.gz` of `/data`, consistent SQLite snapshot via
  `VACUUM INTO`) with a version guard that refuses to start on a
  manifest/binary version mismatch. Per-domain export/import for moving a
  single domain between hosts without re-issuing DNS records.
- Deployment: Docker image + compose, reverse-proxy fragments for Apache
  (default), nginx, Caddy, and Traefik; CI workflow publishing tagged,
  multi-arch images to `ghcr.io` on `vX.Y.Z` tags.
- Security pass against spec 7.6 (exec safety, config-write sanitization,
  server-side validation, rate limiting, session/cookie hardening, output
  escaping, non-root panel) — full compliance, no code changes required.
- Live production deployment on `selfpost.example.com` with a real Let's
  Encrypt certificate; end-to-end delivery confirmed (DKIM pass, SPF pass).