---
title: Global Error Code Reference
description: "Use this as a first-pass decoder before going to the detailed module sections."
url: "https://peikly.com/docs/global-error-code-reference/"
updated: "2026-10-10"
category: Troubleshooting
tags:
  - Manual sync
---

# Global Error Code Reference

Use this as a first-pass decoder before going to the detailed module sections.

## SMTP Errors

| Code or Pattern | Meaning | First Fix |
| --- | --- | --- |
| `421` | Mail server temporarily unavailable | Retry later and check provider status |
| `450` / `451` | Temporary mailbox or provider issue | Retry later; reduce send volume if needed |
| `535` / `5.7.1` | Authentication failed | Re-enter credentials or regenerate the key/password |
| `550` / `5.1.1` | Sender or recipient not accepted | Verify sender identity and recipient address |
| `552` | Message too large | Reduce attachment size |
| `554` | Policy, spam, or reputation rejection | Review SPF, DKIM, DMARC, sender reputation, and content |

## WhatsApp Errors

| Error or State | Meaning | First Fix |
| --- | --- | --- |
| Template rejected | Meta refused the template content or category | Review the rejection reason and resubmit |
| Session expired | More than 24 hours since the last inbound customer message | Reopen the conversation with an approved template |
| Phone not connected | The WhatsApp number is disconnected in Meta | Verify phone status in WhatsApp Manager |
| Message failed to send | API or delivery issue | Check number format, template approval, and Meta status |

## API and Integration Errors

| Code | Meaning | First Fix |
| --- | --- | --- |
| `401` | Missing, invalid, or expired authentication | Recheck token and authorization header |
| `403` | Feature, scope, or permission denied | Confirm plan, role, or token scope |
| `429` | Rate limit reached | Back off and retry later |

## Where to Go Next

- For email delivery problems, continue to [10. Email](/docs/email/).
- For WhatsApp delivery problems, continue to [9. WhatsApp](/docs/whatsapp/).
- For integration failures, continue to [21. External Integrations](/docs/external-integrations-api-guide/).
- For cross-feature diagnosis, use [24. Global Troubleshooting Guide](/docs-category/troubleshooting-help/).