HTML version: https://cooperemail.com/guides/openai-codex-agent-email-inbox

Codex

# Give an OpenAI Codex agent its own email inbox

Yes, Cooper Email gives an OpenAI Codex agent its own inbox with one POST to https://cooperemail.com/api/v1/onboard, which returns an API key once and username@cooperemail.com. Save that key, then add the hosted MCP server at https://cooperemail.com/mcp in ~/.codex/config.toml. Free: $0, no card, 5 inboxes, 5,000 emails/month, and no separate daily cap.

```
curl -s 'https://cooperemail.com/api/v1/onboard?ref=codex-page' \
  -H 'content-type: application/json' \
  -H 'X-Client: curl' \
  -d '{"username":"codex-agent","display_name":"Codex"}'
```

## Connect Codex to that inbox

Replace coop_live_YOUR_KEY with the api_key from the signup response. The key is shown once. This is the manual MCP config for ~/.codex/config.toml. Codex CLI 0.165.0 can also install this same server with the plugin commands on https://cooperemail.com/for/codex. Those commands do not put the key in the shell. If Codex is already connected and has no key, call cooper_onboard with username codex-agent. This page does not use codex mcp add, which waits for a browser sign-in.

```
# ~/.codex/config.toml
[mcp_servers.cooper-email]
url = "https://cooperemail.com/mcp"

[mcp_servers.cooper-email.http_headers]
Authorization = "Bearer coop_live_YOUR_KEY"
```

[Codex plugin install](/for/codex) · [MCP](/docs/mcp) · [Pricing](/pricing) · [Docs](/docs) · [llms.txt](/llms.txt)

Operator: Avatar 8 LLC (ops@avatar33.com).

Agents ask

## FAQ

### How do I give an OpenAI Codex agent its own email inbox?

POST [https://cooperemail.com/api/v1/onboard](https://cooperemail.com/api/v1/onboard) with {"username":"codex-agent"}. Cooper Email returns an API key once and codex-agent@cooperemail.com. No card and no dashboard. Then set that key as the Authorization bearer for [https://cooperemail.com/mcp](https://cooperemail.com/mcp) in ~/.codex/config.toml.

### What if the username codex-agent is already taken?

POST /api/v1/onboard returns HTTP 409 inbox_exists when that username is taken. Pick another name that still starts with codex-, or check first with GET [https://cooperemail.com/api/v1/usernames/check?name=codex-agent.](https://cooperemail.com/api/v1/usernames/check?name=codex-agent.) The check does not say who holds a name.

### Does Codex need the plugin before it can have an inbox?

No. The signup request creates the inbox. The plugin commands on [https://cooperemail.com/for/codex](https://cooperemail.com/for/codex) install the hosted MCP server and the agent-email and human-in-the-loop skills, and they do not put an API key in the shell. The toml on this page is how Codex uses the key from signup.

### What does Cooper Email Free include for a Codex agent?

Free: $0, no card, 5 inboxes, 5,000 emails/month, and no separate daily cap. Custom domains are not included on Free (0). They start on Starter ($12/month).

[More answers on the FAQ](/faq)