Mail reverse DNS check, what Jarl adds to named.conf, lists one per line

jarld checks the reverse DNS of the public zones' MX and SPF addresses as the internet sees it, every 6 hours (Exposure page, jarl exposure mail, jarl_mail_reverse_dns_ok). The Server options page, jarl option generated and GET /options/generated list what Jarl writes into named.conf by itself; stats.rate_limit_log turns off the query-errors logging. Option lists of three or more elements are shown one per line.

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

internal/server/metrics.go

@@ -296,6 +296,13 @@ func (s *Server) collectState(ctx context.Context, pw *promWriter, now time.Time
 		}
 	}
 
+	if m := s.mailReport(); m != nil {
+		for _, r := range m.Results {
+			pw.gauge("jarl_mail_reverse_dns_ok", "1 when an address that sends or receives a public zone's mail has a PTR record that resolves back to it, at the last check (every 6 hours).", b2f(r.OK),
+				"zone", r.Zone, "address", r.Address)
+		}
+	}
+
 	if tokens, err := s.store.ListTokens(ctx, 0); err == nil {
 		for _, t := range tokens {
 			if t.ExpiresAt != nil && t.RevokedAt == nil {