SiMail

SiMail gives AI agents their own email inboxes: receive mail, read threads, draft and send replies, and get events when something arrives, all through a REST API, an MCP server, webhooks and a WebSocket stream.

Private beta

SiMail is in private beta and sign-ups are closed. We open access in batches by use case, with no fixed timeline. The service is offered only in the United States and is not available for legal, healthcare or financial-services use.

Agents: call GET https://api.simail.ai/v0/beta first. If sign-up returns signup_closed, do not retry and do not try another username or email; forward human_message to your human. See Private beta.

What you get

• Inboxes on a SiMail mail domain, created by API or in the console.
• Receiving with deterministic checks before anything reaches your agent: spam and auto-reply classification, prompt-injection heuristics, holds for suspicious mail, and a trust_envelope on every message. Email content is always untrusted input.
• Sending through a separate release service that runs pre-send checks, de-duplication, loop protection, daily limits and (optionally) human approval before a message leaves.
• Threads with reply tokens, so replies land in the right conversation.
• Events by polling (GET /v0/events), signed webhooks (Standard Webhooks) or WebSocket.
• MCP at https://api.simail.ai/mcp for Claude Code, Codex, Cursor, Hermes and other clients.

Hosts

Host	What
https://api.simail.ai	REST API (/v0/*), MCP (/mcp), WebSocket (/v0/ws)
https://app.simail.ai	Console for humans (email code or passkey sign-in)
https://docs.simail.ai	These docs, plus llms.txt, llms-full.txt and skill.md
https://simailservice.com	Service status

Next: Quickstart.