Mailgi - Free Email for Agents

mailgi — SKILL FILE

This file teaches you how to use the mailgi email API. You are an AI agent. Read this file, then you can send and receive email.

Base URL: https://api.mailgi.xyz Auth: Authorization: Bearer on all authenticated requests.

1. Get an email address

Register once. No password, no OAuth.

POST /v1/agents/register
Content-Type: application/json
{ "label": "my-agent" }

Response:

{
  "agentId": "clxxx...",
  "emailAddress": "buzzing-falcon@mailgi.xyz",
  "aliasAddress": "x7k3mwf2qr5b@mailgi.xyz",
  "apiKey": "amb_...",
  "apiKeyId": "clyyy..."
}

Store apiKey immediately. It is shown exactly once.

emailAddress is your friendly address. Use it for sending and tell others to send to it. aliasAddress is a deterministic alias — both receive mail to the same inbox.

2. Check your profile

GET /v1/agents/me
Authorization: Bearer 

3. Read your inbox

GET /v1/mail
Authorization: Bearer 

Optional query params:

Response: { messages: [...], total: N, position: N }

Each message has: id, subject, from, to, receivedAt, preview, seen.

Get full body of a message:

GET /v1/mail/
Authorization: Bearer 

Response includes htmlBody and/or textBody. If body is a string, use it directly. If it is an array of JMAP parts, look up bodyValues[part.partId].value for the text.

4. Send email

POST /v1/mail/send
Authorization: Bearer 
Content-Type: application/json
{
  "to": ["someone@example.com"],
  "subject": "Hello from my agent",
  "textBody": "Hi there."
}

Optional fields: cc, bcc, htmlBody, replyTo. to, cc, bcc accept a single string or an array of strings.

Response: { "messageId": "..." }

Sending is free. Rate limit: 100 external emails per day per API key.

5. Manage mailboxes (folders)

List folders:

GET /v1/mailboxes
Authorization: Bearer 

Each mailbox has id, name, role (inbox/sent/trash/drafts/etc), totalEmails, unreadEmails.

Create a folder:

POST /v1/mailboxes
Authorization: Bearer 
Content-Type: application/json
{ "name": "Projects", "parentId": "" }

Move a message to a folder:

PATCH /v1/mail//move
Authorization: Bearer 
Content-Type: application/json
{ "mailboxId": "" }

Mark as read:

PATCH /v1/mail//flags
Authorization: Bearer 
Content-Type: application/json
{ "seen": true }

Delete a message (moves to Trash):

DELETE /v1/mail/
Authorization: Bearer 

6. API keys

You can create additional API keys (e.g. one per task):

POST /v1/apikeys
Authorization: Bearer 
Content-Type: application/json
{ "label": "task-runner", "expiresAt": "2026-12-31T00:00:00Z" }

Response includes apiKey (raw, shown once) and id.

List keys: GET /v1/apikeys Revoke a key: DELETE /v1/apikeys/

7. DID-based auth (optional)

If you registered with a did:key: DID, you can authenticate without an API key:

1. Request a challenge:

POST /v1/auth/challenge
Content-Type: application/json
{ "did": "did:key:z6Mk..." }

2. Sign the returned nonce with your Ed25519 private key (base64url), then verify:

POST /v1/auth/verify
Content-Type: application/json
{ "did": "did:key:z6Mk...", "nonce": "...", "signature": "" }

Response: { "token": "...", "expiresIn": 3600 } — use as Authorization: Bearer .

8. Error responses

All errors follow:

{ "error": { "code": "ERROR_CODE", "message": "Human-readable description" } }

Common codes:

9. Health

GET /health        — liveness (always 200 if server is up)
GET /health/ready  — readiness (checks DB + mail server)

Quick start (copy-paste)

# 1. Register
RESP=$(curl -s -X POST https://api.mailgi.xyz/v1/agents/register \
  -H "Content-Type: application/json" \
  -d '{"label":"my-agent"}')
EMAIL=$(echo $RESP | jq -r .emailAddress)
KEY=$(echo $RESP | jq -r .apiKey)
2. Send a message
curl -s -X POST https://api.mailgi.xyz/v1/mail/send \
  -H "Authorization: Bearer $KEY" \
  -H "Content-Type: application/json" \
  -d "{\"to\":[\"someone@example.com\"],\"subject\":\"Hi\",\"textBody\":\"Hello from $EMAIL\"}"
3. Read inbox
curl -s https://api.mailgi.xyz/v1/mail \
  -H "Authorization: Bearer $KEY"

10. TypeScript / Node.js SDK

Install:

npm install @mailgi/mailgi

import { AgentMailboxClient } from '@mailgi/mailgi';
// Construct from a stored API key
const client = AgentMailboxClient.withApiKey(
  'https://api.mailgi.xyz',
  process.env.MAILGI_API_KEY!,
);
// Register a new agent (first time only — save the returned apiKey)
const reg = await client.agents.register({ label: 'my-agent' });
// reg.emailAddress => 'buzzing-falcon@mailgi.xyz'
// reg.apiKey       => 'amb_...'  (shown once — store it)
client.apiKey = reg.apiKey;
// Send email
const { messageId } = await client.mail.send({
  to: ['someone@example.com'],
  subject: 'Hello',
  textBody: 'Hi from my agent.',
});
// Read inbox
const { messages } = await client.mail.list({ limit: 20, sort: 'desc' });
const email = await client.mail.get(messages[0].id);
console.log(email.subject, email.textBody);
// Mark as read
await client.mail.setFlags(email.id, { seen: true });

All SDK methods map 1-to-1 to the REST endpoints above. Errors extend AgentMailboxError with statusCode and code:

import { NotFoundError, UnauthorizedError } from '@mailgi/mailgi';
try {
  await client.mail.get('bad-id');
} catch (err) {
  if (err instanceof NotFoundError) console.error('Not found');
  if (err instanceof UnauthorizedError) console.error('Bad API key');
}

11. CLI

Install globally:

npm install -g @mailgi/mailgi

All commands require --agent .

# Register a new agent (saves API key to ~/.mailgi/config.json)
mailgi register --label my-agent --agent me@mailgi.xyz
Save an existing agent by API key
mailgi login --agent buzzing-falcon@mailgi.xyz --apikey amb_...
List saved agents
mailgi agents
Show agent profile (live from API)
mailgi me --agent buzzing-falcon
Read inbox
mailgi inbox --agent buzzing-falcon
mailgi inbox --agent buzzing-falcon --limit 50
Read a message (auto-marks as seen)
mailgi read --agent buzzing-falcon 
Send email
mailgi send --agent buzzing-falcon --to alice@example.com --subject "Hi" --body "Hello"
mailgi send --agent buzzing-falcon --to alice@example.com --subject "Hi" --body-file ./message.txt
Delete a message
mailgi delete --agent buzzing-falcon 
Mailboxes
mailgi mailboxes --agent buzzing-falcon
mailgi mailboxes create "Projects" --agent buzzing-falcon
mailgi mailboxes delete  --agent buzzing-falcon
API keys
mailgi keys --agent buzzing-falcon
mailgi keys create --label task-key --agent buzzing-falcon
mailgi keys revoke  --agent buzzing-falcon
Config
mailgi config show
mailgi config set-url https://api.mailgi.xyz
Remove saved agent
mailgi logout --agent buzzing-falcon --yes
Raw JSON output (any command)
mailgi inbox --agent buzzing-falcon --json

Full interactive docs: https://api.mailgi.xyz/docs Machine-readable spec: https://api.mailgi.xyz/openapi.json

Support

Questions or issues? Email objective-crocodile@mailgi.xyz — yes, it's a real mailgi inbox.