## Context
bd code-vnc investigated why `viktorbarzin/dovecot_exporter` only
exposed `dovecot_up{scope="user"} 0`. Root cause: the exporter speaks
the legacy pre-2.3 `old_stats` FIFO wire protocol. docker-mailserver
15.0.0 ships Dovecot 2.3.19, which moved to `service stats` with a
different architecture — `doveadm stats dump` on the old-stats
unix_listener returns "Failed to read VERSION line" and the exporter
loops on "Input does not provide any columns".
Attempted fix: enabled `old_stats` plugin via `mail_plugins` +
declared `service old-stats { unix_listener stats-reader }`. Socket
was created but protocol incompatibility made it useless. Reverted.
## This change
- Reverts the attempted dovecot.cf additions
- Adds a comment in the dovecot.cf heredoc explaining why we
deliberately do NOT enable old_stats here
- `auth_failure_delay = 5s` (code-9mi) and
`mail_max_userip_connections = 50` stay — they're unrelated to
stats
## What is NOT in this change
- A replacement exporter — filed as follow-up bd code-1ik with
two paths: switch to jtackaberry/dovecot_exporter, or retire the
exporter+scrape+alert entirely
- The `mailserver-metrics` ClusterIP Service (from code-izl) —
kept; it will be useful for whichever path code-1ik chooses
## Test Plan
### Automated
```
$ kubectl exec -n mailserver -c docker-mailserver deployment/mailserver -- \
supervisorctl status dovecot postfix
dovecot RUNNING pid 1022, uptime 0:00:27
postfix RUNNING pid 1063, uptime 0:00:26
$ kubectl rollout status deployment/mailserver -n mailserver
deployment "mailserver" successfully rolled out
```
### Manual Verification
Dovecot config returns to baseline + auth_failure_delay. Mail continues
to flow (E2E probe continues to succeed via `email-roundtrip-monitor`).
Closes: code-vnc
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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