release: 2.7.0: base-trixie - Debian trixie, Postfix 3.10.13

Cut without asking, as the owner said on 2026-10-15.

The image runs debian:trixie-slim with Postfix 3.10.13, libmilter
8.18.1, OpenSSL 3.5; every citation re-read against the trixie sources.
smtpd_hide_client_session=yes on 465/587 (owner's decision). The
selfpost group is 10998 and the panel 10999:10999, outside the system
range; the entrypoint re-owns /data by name. The panel's database is
0600; the entrypoint removes symbolic links the panel could leave under
/data. Commits 68ec8b2, 1c6e04b, a3050af.

Rolled out to the test server as 2.6.1-post.a3050af (the same code),
2026-10-15 17:07 UTC: healthy, every program RUNNING, no restarts, three
messages sent, the queue empty, no warning but outside password guessing.
The canary: one message from an application through 465 to Gmail, Yandex
and the test mailbox - Received: in the short form everywhere; Gmail
dkim=pass spf=pass dmarc=pass; Yandex spf=pass dkim=pass, not spam.
No migration, schema 11.

CHANGELOG cut; pin 2.7.0 in deploy/docker-compose.yml, README, guide (and
its sample restore message); development.md "from pin" and the rows of
base-trixie and panel-dkim-signing; roadmap row and recommended order.
No tag.

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

CHANGELOG.md

@@ -5,6 +5,15 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/); version
 
 ## [Unreleased]
 
+## [2.7.0] - 2026-10-15
+
+The image runs Debian trixie and Postfix 3.10.13, with upstream's 2026
+security fixes that bookworm will not get. The `Received:` header no
+longer shows where an application runs. The container's `selfpost` group
+is 10998 and the panel user 10999: **on upgrade, `chgrp 10998` the TLS
+private key in `certs/` on the host** (a certbot deploy hook too). The
+panel's database is the panel's alone. No migration; schema 11.
+
 ### Security
 
 - **The panel's database was readable by every user of the container.**