Show this Postfix's retry policy on Mail queue and delivery history.

Numbers come from a one-shot postconf -h at panel start so a manual override is visible after restart, without inventing an attempt count.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/postfix/retry.go

@@ -0,0 +1,135 @@
+package postfix
+
+import (
+	"fmt"
+	"log"
+	"os/exec"
+	"strings"
+	"time"
+)
+
+// RetryPolicy is this Postfix's deferred-mail retry timings, as postconf
+// reports them. The panel loads it once at HTTP start (architecture.md) and
+// never re-reads it for a request.
+type RetryPolicy struct {
+	QueueRunDelay        time.Duration
+	MinimalBackoff       time.Duration
+	MaximalBackoff       time.Duration
+	MaximalQueueLifetime time.Duration
+	BounceQueueLifetime  time.Duration
+	DelayWarningTime     time.Duration
+	// FromDefaults is true when postconf could not be read and the compiled-in
+	// Postfix 3.x values were substituted. The Mail queue card shows a muted
+	// note in that case so an operator who overrode the parameters is not
+	// silently shown the stock numbers.
+	FromDefaults bool
+}
+
+// DefaultRetryPolicy is Postfix 3.x compiled-in values for the six parameters
+// build/postfix-config.sh does not set. Used when postconf is missing (unit
+// tests, a binary outside the container) so the panel still starts.
+func DefaultRetryPolicy() RetryPolicy {
+	return RetryPolicy{
+		QueueRunDelay:        300 * time.Second,
+		MinimalBackoff:       300 * time.Second,
+		MaximalBackoff:       4000 * time.Second,
+		MaximalQueueLifetime: 5 * 24 * time.Hour,
+		BounceQueueLifetime:  5 * 24 * time.Hour,
+		DelayWarningTime:     0,
+		FromDefaults:         true,
+	}
+}
+
+// retryConfKeys is the fixed argv tail for `postconf -h`. Order matches the
+// fields of RetryPolicy. No user input is interpolated (security.md).
+var retryConfKeys = []string{
+	"queue_run_delay",
+	"minimal_backoff_time",
+	"maximal_backoff_time",
+	"maximal_queue_lifetime",
+	"bounce_queue_lifetime",
+	"delay_warning_time",
+}
+
+// readRetryConf runs `postconf -h` for the retry-policy keys. Tests replace it
+// the same way logtail stubs queueIDs.
+var readRetryConf = postconfRetryValues
+
+func postconfRetryValues() ([]string, error) {
+	// Fixed argv, no user input — same pattern as Queue (security.md).
+	cmd := exec.Command("postconf", "-h",
+		"queue_run_delay",
+		"minimal_backoff_time",
+		"maximal_backoff_time",
+		"maximal_queue_lifetime",
+		"bounce_queue_lifetime",
+		"delay_warning_time",
+	)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return nil, fmt.Errorf("postconf -h: %w: %s", err, strings.TrimSpace(string(out)))
+	}
+	lines := strings.Split(strings.TrimSpace(string(out)), "\n")
+	if len(lines) != len(retryConfKeys) {
+		return nil, fmt.Errorf("postconf -h: got %d values, want %d", len(lines), len(retryConfKeys))
+	}
+	for i := range lines {
+		lines[i] = strings.TrimSpace(lines[i])
+	}
+	return lines, nil
+}
+
+// LoadRetryPolicy reads the effective Postfix retry parameters. On any failure
+// it logs a warning and returns DefaultRetryPolicy; the HTTP role must not
+// refuse to start because postconf is absent.
+func LoadRetryPolicy() RetryPolicy {
+	lines, err := readRetryConf()
+	if err != nil {
+		log.Printf("postfix: retry policy: %v; using compiled-in defaults", err)
+		return DefaultRetryPolicy()
+	}
+	p, err := parseRetryPolicy(lines)
+	if err != nil {
+		log.Printf("postfix: retry policy: %v; using compiled-in defaults", err)
+		return DefaultRetryPolicy()
+	}
+	return p
+}
+
+func parseRetryPolicy(lines []string) (RetryPolicy, error) {
+	if len(lines) != len(retryConfKeys) {
+		return RetryPolicy{}, fmt.Errorf("got %d values, want %d", len(lines), len(retryConfKeys))
+	}
+	var durs [6]time.Duration
+	for i, line := range lines {
+		d, err := ParseDuration(line)
+		if err != nil {
+			return RetryPolicy{}, fmt.Errorf("%s: %w", retryConfKeys[i], err)
+		}
+		durs[i] = d
+	}
+	return RetryPolicy{
+		QueueRunDelay:        durs[0],
+		MinimalBackoff:       durs[1],
+		MaximalBackoff:       durs[2],
+		MaximalQueueLifetime: durs[3],
+		BounceQueueLifetime:  durs[4],
+		DelayWarningTime:     durs[5],
+	}, nil
+}
+
+// FirstRetry is the human string for the first deferred retry (minimal
+// backoff), shared by the Mail queue card and delivery history.
+func (p RetryPolicy) FirstRetry() string {
+	return FormatDuration(p.MinimalBackoff)
+}
+
+// BackoffCap is the human string for maximal_backoff_time.
+func (p RetryPolicy) BackoffCap() string {
+	return FormatDuration(p.MaximalBackoff)
+}
+
+// QueueLifetime is the human string for maximal_queue_lifetime.
+func (p RetryPolicy) QueueLifetime() string {
+	return FormatDuration(p.MaximalQueueLifetime)
+}