panel-notifications: findings of the technical and security reviews

Neither review (read-only agents, Opus and Fable, over 972a9f8..400aa76) has
a Critical finding. Both found the same serious one, and more:

- The notification about refused mail was built on what a rejected row says
  of itself. Its domain is the one in MAIL FROM, which the client typed and
  Postfix has not yet held against the login when the milter refuses: an
  application over its limit could have had the panel write a message per
  made-up domain, to another tenant's users among others. And the same
  status is written when an application is refused for its client address,
  which is no limit. Refusals are now counted by the domain the login is
  registered under, only for logins that exist and only while a limit is set
  on the login or its domain; one subject per sending domain. They are read
  through a partial index of their own (migration 0005): the query walked
  the whole send log every minute.
- Account and user e-mails were checked with the DMARC report validator,
  which refuses Gmail and the like - the owner's own kind of address. A new
  validate.AccountEmail accepts them and refuses a local part beginning "-".
- "Said" now means sent: what arises while nobody can be told, or while
  Postfix does not take the message, is told at a later check. Its ending
  with nobody left to tell is simply over.
- Two DNS checks must be 45 minutes apart as well as two: the last check
  before a restart and the first after it were minutes apart.
- The notifier's own mail waiting in the queue, and its bounce coming back
  to postmaster@ this server, are not the queue's subject. A listing cut at
  its size limit or with a line too long to read is no listing; postqueue -j
  gets 30 seconds.
- The tables must name the selector the panel shows, not only have the line.
- An a/mx lookup that did not answer inside the SPF check made the record
  "not authorising"; it is "cannot tell" now, for the pages too.
- A ceiling of 60 messages an hour; a pass stops between domains when the
  process is asked to stop; sendmail gets a WaitDelay; days are rounded as a
  person counts; a failed read of the switch shows it on, not off.

Recorded as accepted in security.md, with a roadmap candidate
(from-header-binding): an application can have a message signed as the
server's own name - or, as always, as another registered domain - by writing
it into the From: header, which nothing holds against the login.

Left as found: a recipient whose copy failed while another's went out is not
tried again; a certificate that lives under 14 days is reported at each
renewal.

On the test server, for this tree: go vet clean, go test ./... 23 packages
ok, make e2e ok (326 s).

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

CHANGELOG.md

@@ -15,7 +15,7 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/); version
 - **The panel writes to its users when something needs them.** Four things,
   each said once: a sending domain's DKIM, SPF or DMARC record stops matching
   (after two hourly checks in a row, and once more when it matches again); a
-  level-2 rate limit refuses mail (at most once a day per limit); the TLS
+  level-2 rate limit refuses mail (at most once a day per sending domain); the TLS
   certificate is 14 days from expiry, and 3; a message has waited in the
   queue for more than three days (and once more when none has). Global users
   are told all of it, domain users about their own domains. Sent from
@@ -24,7 +24,7 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/); version
 - **The server's own name is signed.** The panel generates a DKIM key for
   `SELFPOST_HOSTNAME` and OpenDKIM signs mail submitted locally as that name
   (`non_smtpd_milters`), so that notifications arrive. The name is not a
-  sending domain: no application can send as it.
+  sending domain: no application can use it as an envelope sender.
 - **Notifications in the panel.** Account has *Send me notifications* beside
   the e-mail; Server › Settings has the switch for everyone and the two DNS
   records of the server's own name, DKIM and SPF, with the values to publish;
@@ -32,6 +32,27 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/); version
   has a Notifications topic. Every user starts with notifications on, and so
   does the instance.
 
+### Changed
+
+- **An account e-mail may be at a public mail host.** Account and Server ›
+  Users refused addresses at Gmail, Outlook, Proton and the like, a rule that
+  belongs to DMARC report addresses. A user's own address is now where the
+  panel writes to them.
+- **A lookup that does not answer is not an SPF mismatch.** When the address
+  lookup behind an `a` or `mx` mechanism timed out, a domain's SPF record was
+  shown as not authorising this server. It is now a warning that the check
+  could not tell.
+
+### Security
+
+- Technical and security reviews of 2026-10-12 of the notifications, before
+  release: no Critical finding. The notification about refused mail was built
+  on the domain a client writes in `MAIL FROM`; it is now built on the
+  registry. Recorded in [security.md](docs/security.md) as accepted, with a
+  roadmap candidate (from-header-binding): an application can have a message
+  signed as another registered domain, or as the server's own name, by
+  writing it into `From:` - the first part of which has always been so.
+
 ## [2.2.0] - 2026-10-12
 
 ### Added