Billionmail/BillionMail · warning

open maildirsize failed: %w

Error message

open maildirsize failed: %w

What it means

readMaildirsize opens the 'maildirsize' file inside a user's maildir to compute used quota space; this error wraps any os.Open failure (missing file or permission denied) when updating a mailbox's used space. It means the used-space calculation could not read its data source for that user.

Source

Thrown at core/internal/service/mail_boxes/update_used_space.go:194

		} else {
			if err := tx.Commit(); err != nil {

				failCount += len(batch)
			} else {
				successCount += batchSuccess
			}
		}
	}

	//g.Log().Debug(ctx, "Batch update completed", "success", successCount, "failed", failCount)
}

func readMaildirsize(userDir string) (int64, error) {
	path := filepath.Join(userDir, "maildirsize")

	f, err := os.Open(path)
	if err != nil {
		return 0, fmt.Errorf("open maildirsize failed: %w", err)
	}
	defer f.Close()

	scanner := bufio.NewScanner(f)
	var total int64
	var lineNo int

	for scanner.Scan() {
		lineNo++
		line := strings.TrimSpace(scanner.Text())

		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}

		parts := strings.Fields(line)
		if len(parts) == 0 {
			continue

View on GitHub (pinned to fc36c76c05)

Solutions

1. Verify the user's maildir exists and contains a maildirsize file; send a test mail or let Dovecot initialize quotas
2. Check file ownership/permissions so the BillionMail process can read the maildir
3. Confirm the userDir path passed to readMaildirsize is correct for that mailbox
4. Treat missing maildirsize as zero usage upstream if that is acceptable for your setup

if _, err := os.Stat(filepath.Join(userDir, "maildirsize")); os.IsNotExist(err) {
    // maildir not initialized; treat used space as 0 or skip
}

if err != nil && strings.Contains(err.Error(), "open maildirsize failed") {
    if os.IsNotExist(errors.Unwrap(err)) {
        // default used space to 0 and continue
    }
}

When it happens

Trigger: Calling the used-space update path (anonymous caller) for a user directory that has no maildirsize file, or one the process cannot read (wrong ownership/permissions).

Common situations: Mailbox created but never received mail (maildirsize not yet created by Dovecot); maildir mounted/copied with wrong ownership; user directory path computed incorrectly.

Understand the failure class

Background: "File not found" and ENOENT errors: why libraries can't find a file that should exist — this error's family across 50 libraries.

Related errors

• parse maildirsize line %d: invalid size '%s': %w
• project configuration file does not exist: %s
• error reading project configuration file: %v
• error writing project configuration file: %v
• error creating project configuration: %v

AI-assisted analysis of Billionmail/BillionMail@fc36c76c05 (2026-09-05). Data as JSON: /api/errors/e8305d1afe9ba920. Report an issue: GitHub.