chore: initial import from KNEL/PFVCluster@041d311 [#769]

Split per O&M lane work order. Full history: KNEL/PFVCluster.
https://projects.knownelement.com/issues/769#note-4152

mail/README.md

@@ -0,0 +1,21 @@
+# netinfra/mail — PMG / fleet mail tooling
+
+Pointers + usage. Knowledge doc (map, findings, deploy plan):
+[Discourse t/322 — Mail environment map + PMG deploy plan](https://community.turnsys.com/t/322).
+Ticket: [Redmine #696](https://projects.knownelement.com/issues/696).
+
+## Files
+
+- `audit-mail-env.sh` — read-only mail probe, runs ON a target
+  (postfix config, alt relays, identity, :25 listeners, relay log
+  evidence). Delivered via the ssh chokepoints only
+  (`remote.sh prox-file|vm-file`, `remote-dns.sh <host>-file`).
+- `run-mail-audit.sh` — drives the probe across
+  `audit-targets.txt`; output per host under `.crush/audit/mail/`.
+- `audit-targets.txt` — fleet target list (`mode|name|user`).
+
+## Re-run the audit
+
+```bash
+bash netinfra/mail/run-mail-audit.sh
+```