For AI agents: a documentation index is available at the root level at /llms.txt and /llms-full.txt. Append /llms.txt to any URL for a page-level index, or .md for the markdown version of any page.
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DocumentationAPI ReferenceKnowledge BaseChangelog
DocumentationAPI ReferenceKnowledge BaseChangelog
    • Introduction
  • Getting Started
    • What is AgentMail?
    • What can I do with an inbox?
    • Creating your first inbox
    • Getting your API key
  • Agent Patterns
    • Handling inbound emails
    • Allowlists & blocklists
    • Managing threaded conversations
    • Human-in-the-loop workflows
    • Pods for multi-tenant email
    • Using labels to track state
  • Domains & Deliverability
    • Custom domain setup
    • SPF, DKIM, and DMARC setup
    • Emails going to spam
    • Warming Up
    • MX record conflicts
  • Troubleshooting
    • API 403 error
    • Rate limits
    • Preventing duplicate sends
    • Domain not verifying
    • Emails bouncing
    • Why are my emails not showing up?
  • DNS Guides
    • Cloudflare
    • GoDaddy
    • Route 53 (AWS)
    • Namecheap
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On this page
  • 1. Incorrect API key
  • 2. Accessing a resource you do not own
  • 3. Missing required parameters
  • 4. Sending to a suppressed address
  • We do not restrict your API key
  • Test your API key
  • Still getting 403?
Troubleshooting

What does a 403 error mean?

Common causes of API 403 Forbidden errors and how to fix them.
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A 403 Forbidden response from the AgentMail API means your request was rejected. This can happen for several reasons, and the fix depends on the cause.

1. Incorrect API key

The most common cause. Your API key may be missing, incomplete, or invalid.

How to fix:

  • Go to the AgentMail Console and generate a new API key
  • When you generate a new key, copy the entire key immediately. It is only shown once and starts with am_
  • Make sure you are passing the key in the Authorization header as Bearer am_...
TypeScript
1import { AgentMailClient } from "agentmail";
2
3// Make sure the full key is copied, no trailing spaces or missing characters
4const client = new AgentMailClient({ apiKey: "am_..." });

A common mistake is copying only part of the key. API keys are long strings. Double check that you copied the complete value from start to finish.

2. Accessing a resource you do not own

You will get a 403 if you try to access an inbox, message, thread, or domain that belongs to a different organization. Each API key is scoped to one organization, and you can only access resources created under that organization.

How to fix: Verify that the inbox_id, message_id, thread_id, or domain_id in your request actually belongs to your account.

3. Missing required parameters

Some endpoints return a 403 when required path parameters are missing or malformed. For example, calling /v0/inboxes//messages with an empty inbox_id may return 403 instead of 400.

How to fix: Double check that all required path parameters are filled in correctly.

4. Sending to a suppressed address

AgentMail automatically suppresses addresses that have previously bounced, been rejected, or filed a spam complaint. If you try to send to a suppressed address, the API returns a 403.

How to fix: Check if the recipient address has been suppressed. See Emails bouncing for more details on how suppression works.

We do not restrict your API key

AgentMail does not place any feature restrictions on your API key. Every API key has access to all endpoints. If you are getting a 403, it is not because your key lacks permissions. It is one of the causes listed above.

Test your API key

The fastest way to verify your API key is working is to use the Try it feature in our API Reference.

  1. Go to any endpoint in the API Reference
  2. Click Try it in the top right of the code panel
  3. Enter your API key in the Authorization field
  4. Click Send

If you get a 200 response, your key is valid and working. You can then copy the generated code snippet from the panel to use in your application.

Still getting 403?

If none of the above resolves your issue, reach out in our Discord support channel or email support@agentmail.cc with the full error response and the endpoint you are calling.