Documentation
Quickstart, authentication, sending, receiving, threading, agent limits, webhooks, errors, the MCP server, templates, campaigns, automations, topics, approvals and the API reference.
The API is described machine-readably at /openapi.json, with orientation for models at /llms.txt. These pages are the version for people.
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Sending and receiving
Agents
Recipes
Send an email from your agent and read the reply
From Claude Code, Cursor or Codex: send a message over MCP, reply from your own inbox, read the reply back as a thread, and answer on the same thread.
Hold an agent's email for human approval
Give an agent a key that drafts instead of sending, release its drafts as a person, and keep the conversation going with every reply held the same way.
Follow up when nobody replies
Schedule a follow-up on the same thread when you send, and cancel it the moment the person answers, over MCP or REST.
Marketing
Reference
API reference
API overview
Base URL, authentication, scopes, pagination, errors, idempotency and rate limits: what every endpoint has in common.
API overview
Base URL, authentication, scopes, pagination, errors, idempotency and rate limits: what every endpoint has in common.
Emails
Send, schedule, batch, cancel and look up outbound email, with its event timeline and delivery metrics.
Templates
Stored subjects and bodies with {{variable}} placeholders, addressed by slug and rendered with HTML-escaped values.
Approvals
The queue of sends held for a person by keys that require approval, and the call that releases or rejects each one.
Domains
Register the domains you send from, get the DNS records to publish, and check their verification, bounce-path and click-tracking state.
Suppressions
The addresses a workspace refuses to mail, why, and for which kind of mail: look one up, add them singly or in bulk, and lift them.
Inbound
Download the attachments of received mail, which are kept for 30 days after the message arrives.
Threads
Conversations that join outbound mail with the replies it attracts, readable as one transcript and filterable by what still needs an answer.
Webhook endpoints
Subscribe a URL to email events, change or remove the subscription, and see every delivery attempt made to it.
Contacts
The people you mail: find them across every audience, add them to a list, update their names, attributes and subscription, tag them, and delete them.
Contact properties
Declare the custom fields contacts carry in attributes, with a display name and a type that incoming values are coerced to.
Audiences
Lists of contacts: create them, add one person or import up to 5,000 at a time with their opt-out status, page through the members, and remove people.
Segments
Saved, named filters over one audience, by tags, engagement, custom properties and topic subscription, that campaigns target and you can count before sending.
Topics
Categories of marketing mail a person can opt out of one at a time, and each person's preferences across them.
Campaigns
Create, preview, schedule and send a campaign to an audience, run A/B tests, and follow each recipient's outcome.
Automations
Multi-step email sequences that a person is enrolled in once and that end themselves on unsubscribe, reply, suppression, topic opt-out or a tag rule.
Events
Record a named event for one address and start every active automation whose trigger waits on it.
Usage
The workspace's plan, how many emails it has sent this period, what it costs so far, and why a send would be refused right now.
API keys
Create, limit, update and revoke a workspace's API keys, including the per-key guardrails meant for keys an agent holds.