E2a — email for AI agents README

The open-source email API for applications and AI agents.

Send transactional email and give agents real two-way inboxes, with people in control.

Try hosted e2a — start free →

We run the email infrastructure. You connect your app or agent.

Self-host with Docker · Documentation · Agent quickstart · Examples

_{A Token Canopy product · Apache 2.0}

Using a coding agent? Paste this prompt into its chat:

Connect this coding agent to hosted e2a MCP at https://api.e2a.dev/mcp and help me sign in via browser OAuth.

Supports coding agents with remote MCP and browser OAuth. Client setup guide.

Choose how to start

• Hosted — recommended for getting started. Sign up at e2a.dev. Includes the shared agents.e2a.dev domain for instant slug-based onboarding (no DNS setup), a dashboard, the hosted MCP server, and managed deliverability.
• Self-host — run your own infrastructure. See Self-host (Docker) and Deployment. Nearly every feature works the same (content screening is currently self-host-only — see the note below); the shared-domain slug shortcut just needs you to point a mail domain at your relay and set shared_domain in config.yaml.

For application email, start with the transactional email guide. For coding agents, use the prompt above or the setup instructions below.

Quickstart

Connect your agent to hosted e2a

Give your AI agent an inbox directly. Install the e2a plugin — it registers the hosted MCP server and an operate-well skill, so your agent can send, receive, reply in-thread, and hold mail for review out of the box. On first tool use it runs an OAuth flow in your browser — no API key to paste.

Claude Code

claude plugin marketplace add tokencanopy/e2a
claude plugin install e2a@e2a

Codex

codex plugin marketplace add tokencanopy/e2a

Then launch codex, run /plugins, and install e2a.

Cursor — add the MCP server directly. Put this in .cursor/mcp.json (or ~/.cursor/mcp.json to get it in every project); Cursor opens your browser to authorize on first use, no API key to paste:

{
  "mcpServers": {
    "e2a": { "url": "https://api.e2a.dev/mcp" }
  }
}

Other MCP clients (Zed, Goose, Windsurf, Claude Desktop, raw mcp.json) — point straight at https://api.e2a.dev/mcp; ready-to-paste configs are in plugins/e2a/clients/. See plugins/e2a/README.md for the full per-client guide.

What e2a provides

e2a is the open-source email API for applications and AI agents. Any product can send transactional email over HTTP, TypeScript, or Python; agent-native systems can also use real two-way inboxes. Inbound mail arrives with structured SPF, DKIM, and DMARC evidence, and outbound mail can use an optional human-in-the-loop approval gate. Use the hosted service or run the Apache-2.0 stack yourself. No AI agent or agent framework is required for application-triggered sending.

Four ways to plug an agent in:

• MCP — point any MCP-aware runtime at the hosted server (https://api.e2a.dev/mcp) and your agent gets an inbox toolset (list_messages, send_message, reply_to_message, …). The fastest path for agent frameworks. → MCP server
• SDKs — TypeScript (@e2a/sdk) and Python (e2a) clients with one-call webhook verification and a WebSocket listen() stream. → SDKs
• Raw delivery — subscribe a webhook, open a WebSocket, or poll the REST API directly. → Delivery channels
• CLI — e2a listen bridges inbound mail to a local HTTP handler (including an OpenAI Responses auto-reply mode). → CLI

What you get on top of bare SMTP:

• Authenticated inbound identity — normalized SPF, DKIM, and DMARC evidence, with an explicit aligned DMARC verdict
• No public URL required — WebSocket, REST polling, and MCP all work from a laptop or behind a firewall
• Outbound API — agents send to other agents (SMTP relay) or humans (upstream SMTP, e.g. SES, Resend)
• Human in the loop — opt-in approval gate that holds outbound mail until a reviewer approves via dashboard, magic-link email, the MCP tools, or the API
• Inbound threat screening — opt-in content scan flags prompt-injection payloads (hidden HTML, Unicode-tag smuggling, encoded text) — and, with the LLM detector, phishing — then routes each message to allow · review · block, feeding the same review queue as HITL → Content screening. Available on self-hosted deployments; not yet enabled on the hosted service.
• Email reply topology — standards-compliant reply headers plus optional beta thread_id metadata on message reads; caller-owned conversation_id remains application correlation
• Email templates (beta) — reusable {{variable}} templates rendered server-side at send time, plus a pre-built starter catalog → docs/templates.md
• Contacts & outreach (beta) — account-level contact identity (CRUD + bulk import with safe reversal) and per-agent outreach state with server-derived reply/delivery facts, plus the contact.due due-queue notification event → docs/api.md
• Scheduled sending (beta) — send_at on send/reply/forward defers submission up to 90 days ahead; a scheduled send is durable acceptance (status=scheduled) and can be canceled by trashing the message before submission

What you can build

e2a is useful anywhere an AI agent needs a real inbox, persistent email threads, and a safe path from inbound message to outbound action. Start with a complete example:

• Build an AI support agent — triage customer requests, retrieve context, reply in-thread, and hold sensitive replies for approval.

• Build an AI receptionist — answer common inquiries, route messages, and forward conversations to a human team.

• Build an AI scheduling agent — coordinate participants, propose times, and preserve state across multi-turn replies.

• Build an e-commerce agent — answer order questions, handle returns, and coordinate with vendors through persistent email threads.

• Build a sales agent — qualify inbound interest, personalize follow-ups, and keep every conversation moving.

• Build a recruiting agent — coordinate candidates, schedule interviews, and keep hiring workflows in one thread.

• Build a voice follow-up agent — turn a completed call into an email follow-up and keep the conversation going.

• Build a procurement agent — coordinate quotes, purchase orders, and vendor threads with human approval for commitments.

• A support inbox for your AI assistant — give an agent support@yourbrand.com, receive customer mail with SPF/DKIM/DMARC already evaluated as structured evidence, and reply in-thread. Add HITL so anything sensitive waits for a human to approve before it goes out.

• Email between agents — yours and other organizations' — every agent has a real, verified address, so two companies' agents can exchange mail the same way humans do: no new client, protocol, or shared platform to install.

• A personal concierge on your laptop — subscribe over WebSocket (no public URL, no ngrok, no port forwarding), so a local agent can watch an inbox from behind any firewall, triage it, draft replies, and take actions.

• Email-triggered workflows — turn inbound mail into structured events: order confirmations, forms, support tickets, notifications, and receipts rendered server-side from templates, with conversation_id correlated back to your app's state.

• Autopilot with human oversight — an agent drafts outbound mail (newsletters, outreach, reports) and holds each send for one-click approval via magic-link email or the review queue, with automatic expiry policy if no one reviews in time.

Working examples

e2a-runbooks builds several of the above as small, complete, runnable projects — one per agent framework, each demonstrating a different use case and a different part of this API:

They are examples to copy from rather than services to deploy — each says what it simplifies. For the smallest possible signed-webhook reference instead, see the in-repo minimal examples.

How it works

   Human (Gmail/Outlook)  ·  another e2a agent
          │   ▲
  inbound │   │ outbound
    SMTP  ▼   │ upstream SMTP (to humans) / relay (to agents)
   ┌───────────────┐
   │   e2a relay   │  ← MX for your agent domain points here
   │               │
   │   inbound  ↓  │  ← evaluate SPF/DKIM/DMARC · deliver
   │   outbound ↑  │  ← optional HITL hold · send
   └───────────────┘
          │   ▲
  deliver │   │ send · reply · forward (HTTP API)
          ▼   │
   ┌───────────────┐
   │   your agent  │  ← webhook / WebSocket / REST poll / MCP · SDK · CLI
   └───────────────┘

Inbound flow: SMTP → SPF/DKIM/DMARC evaluation → agent lookup → webhook / WebSocket / REST / MCP delivery.

Outbound flow: API call → optional HITL hold → SMTP relay (agent-to-agent) or upstream SMTP (agent-to-human).

Concepts

Delivery channels

Inbound mail reaches you several complementary ways — chosen per integration, not set on the agent. There is no delivery "mode" on the agent record; any agent the caller owns can be consumed over any of these:

Notifications carry lightweight metadata (message id, sender, subject); you fetch the full body + attachments over REST when you want them. A disconnected WebSocket client accumulates "unread" messages; on reconnect, the server drains them as notifications.

Webhooks are an account-level resource (/v1/webhooks), chosen per integration rather than configured on the agent.

Inbound authentication

Inbound messages expose header_from (the parsed RFC 5322 From address), envelope_from (SMTP MAIL FROM), verified_domain (a nullable DMARC-pass convenience projection), and—on detail responses—authentication (SPF, every DKIM signature, and the aligned DMARC result). Reply-To remains separate and never replaces header_from.

For list and review decisions, a non-null verified_domain means DMARC passed for that RFC 5322 From domain. On detail responses, the equivalent check is authentication?.dmarc.status === "pass". Neither field authenticates the mailbox local part, a person, or message content. authentication is null for outbound messages and providerless local loopback delivery.

Before trusting any webhook field, verify the delivery envelope's X-E2A-Signature with the webhook's whsec_… signing secret. The envelope signature covers the complete structured payload, including authentication.

The one-call shortcut parses and verifies a delivery, returning a typed event — use it instead of trusting any field on an unverified payload:

For small signed-webhook references using the ergonomic inbound facade, see the minimal Python and TypeScript OpenAI examples with provider snippets.

from e2a.v1 import construct_event, E2AWebhookSignatureError

# raw request body + the X-E2A-Signature header + your whsec_… secret
try:
    event = construct_event(request_body, signature_header, webhook_secret)
except E2AWebhookSignatureError:
    abort(400)  # bad signature — reject the delivery
if event.type == "email.received":
    email = await client.inbound.from_event(event)
    print(email.envelope_from, email.verified, email.reply_targets)
    result = await email.reply({"text": "Got it"})
    if result.status == "pending_review":
        notify_human(result.message_id)

import { constructEvent, E2AWebhookSignatureError } from "@e2a/sdk/v1";

let event;
try {
  event = constructEvent(req.body, req.header("X-E2A-Signature")!, webhookSecret);
} catch (err) {
  if (err instanceof E2AWebhookSignatureError) return res.status(400).end(); // bad signature
  throw err;
}
if (event.type === "email.received") {
  const email = await client.inbound.fromEvent(event);
  console.log(email.envelopeFrom, email.verified, email.replyTargets);
  const result = await email.reply({ text: "Got it" });
  if (result.status === "pending_review") notifyHuman(result.messageId);
}

construct_event / constructEvent checks that the HMAC matches the canonical signing string and the timestamp is within a 5-minute replay window. Pass an array of secrets to accept either during a rotation: constructEvent(body, header, [oldSecret, newSecret]).

Messages fetched over an authenticated channel — client.messages.get(address, id) or the client.listen(...) stream — are already trusted (the bearer token authenticated the call), so no verify step is needed there.

Email threads and application conversations

Email clients build reply threads from the RFC Message-ID, In-Reply-To, and References graph. Use reply with the original e2a message ID so e2a can emit those headers; a fresh send or forward starts a new email thread.

conversation_id is separate, caller-owned application correlation. Both send and reply accept the optional opaque value, and e2a keeps its existing minting, inheritance, and delivery-correlation behavior when it is omitted. Applications can use it to associate mail with a workflow, ticket, or model session, but reusing it does not join fresh sends into one email thread, and changing it does not split replies out of their RFC thread.

Existing message list and detail responses may also include thread_id (threadId in TypeScript and SDK-shaped CLI JSON). This optional beta field is server-owned, read-only, scoped to one agent mailbox, and derived from reply topology. It is omitted for legacy rows without an assignment. There is no thread_id request field, message filter, or thread list/detail endpoint, and the field is not added to webhook events, WebSocket notifications, exports, or MCP output.

Agent frameworks should bind model memory with conversation_id: create or resume the runtime's internal conversation, pass its stable, non-sensitive session ID (or an opaque stored alias), and scope that binding to the inbox and sender. Continue replying by the original message ID—the correlation value aligns application state, while RFC reply headers preserve the Gmail/Outlook thread. Never treat either identifier as authorization.

Content screening

Inbound email is a prime indirect prompt-injection vector — a message can smuggle instructions aimed at your agent's LLM (hidden HTML, zero-width / Unicode-tag text, encoded payloads) or phish the human behind it. Opt in per agent and e2a inspects message content — subject, plaintext, and both visible and hidden HTML — before your agent ever sees it.

A built-in, dependency-free heuristics detector flags prompt-injection, jailbreak, obfuscation, and data-exfiltration patterns (mapped to OWASP LLM01 / MITRE ATLAS); an optional LLM detector adds semantic injection and phishing classification. Each message gets a verdict — allow · review · block — set by the agent's scan sensitivity (off · low · medium · high): review routes it into the shared HITL queue, block drops it before delivery. Screening is fail-safe — if a detector times out or degrades, the message fails to review, never to a silent allow — and every verdict is written to protection_events for audit and threshold tuning.

Turn it on with PUT /v1/agents/{email}/protection (the same sub-resource as HITL holds), which carries the inbound/outbound × gate/scan posture.

How well does it work? The detection layers are benchmarked in the open: e2a-bench — the evaluation artifact behind the EMNLP 2026 System Demonstrations paper — renders one injection payload across eight structural-hiding surfaces (hidden HTML, multipart mismatch, quoted threads, headers, encodings, PDF attachments) and scores the heuristics engine, open-source classifiers, commercial security APIs, and LLM judges on the same corpus. The per-message judge scores are committed, so the paper's tables reproduce from the artifact alone.

[!NOTE] Content screening is currently available on self-hosted deployments only — it is not yet enabled on the hosted service at e2a.dev. Self-host the image (see Deployment) and set E2A_CONTENT_SCAN_ENABLED=true (off by default even self-hosted — see docs/deployment.md) to use it today.

Human in the loop (HITL)

When an agent's protection config holds an outbound message for review, send and reply calls do not dispatch immediately. The message is stored with status pending_review and the API returns HTTP 202 Accepted. A reviewer must approve it before delivery; otherwise, after a configurable TTL, the protection config's holds.on_expiry decides the terminal: approve (the message just goes out, terminal status sent — for outbound, approving is sending) or reject (discard, review_expired_rejected). (Inbound messages can be held for review too — there, the auto-approve terminal is review_expired_approved, releasing the message to the inbox.)

Reviewers can approve or reject via:

• Dashboard / API — the account-scoped review queue POST /v1/reviews/{id}/approve or /reject (id-addressed, no inbox email needed; lists held items across all the account's inboxes via GET /v1/reviews). This is the only approve/reject path — a review's id is the held message's id.
• MCP tools — approve_review / reject_review (with list_reviews / get_review to find them).
• Magic-link email — sent automatically when a hold fires; one-click GET /v1/approve?t=… and /v1/reject?t=… URLs (requires E2A_PUBLIC_URL and outbound SMTP configured).

Enable review holds on an agent via PUT /v1/agents/{email}/protection: set the outbound gate action to review (or turn on the content scan), plus the hold TTL (holds.ttl_seconds) and its expiry behavior (holds.on_expiry = approve or reject). Posture lives entirely on the protection sub-resource.

API

[!IMPORTANT] The core /v1 API and SDKs are stable and generally available (GA) as of v1.5.0: no breaking changes within /v1. That tag is the compatibility baseline — every later release is audited against it. A small, explicitly enumerated surface is still beta and may change before it is declared stable — contacts & outreach, scheduled sending (send_at), email templates & starter templates, the reviews (HITL) queue, agent protection config, agent-scoped suppressions, managed unsubscribe, message lifecycle diagnostics, delivery metrics, and the thread_id message-read field. Beta surface is marked x-stability-level: beta in the OpenAPI spec and (beta) in the docs; where only specific values of a stable field are beta (the scheduled send status, the screening/review-hold event types, the blocked_by_policy error code), the field carries x-experimental-values naming exactly those values. Everything else is covered by the GA freeze. See the full matrix in docs/api.md → Stability: GA and beta surface. Existing v1.0.x application/cherry-pick tags predate the API freeze and are not /v1 compatibility baselines.

All endpoints are under /v1 unless noted. Auth is Authorization: Bearer <api_key> except for /api/health, /v1/info, /api/feedback, and the HITL magic-link routes. Path parameters containing @ (agent emails) must be URL-encoded.

The surface covers domain registration + verification, agent CRUD, inbound/outbound messages, webhook subscriptions, HITL approve/reject (API key or signed magic-link token), GDPR-style export and deletion, and a WebSocket channel for real-time inbound delivery.

See docs/api.md for the full endpoint reference, or api/openapi.yaml for the machine-readable spec.

MCP server

The fastest way to give an AI-agent runtime an inbox. e2a runs a hosted Model Context Protocol server — point any MCP-aware host (Claude Desktop, Cursor, Cline, Google ADK, LangChain, OpenAI Agents SDK, …) at the Streamable HTTP endpoint:

https://api.e2a.dev/mcp

Authenticate either with OAuth 2.1 (add e2a as a connector and authorize in the browser) or a Bearer API key (Authorization: Bearer <e2a API key>). An agent-scoped credential resolves its agent server-side; account-scoped callers pass the agent email per tool call.

The toolset covers the full agent loop — inbox (list_messages, get_message, get_attachment, list_conversations, get_conversation, update_message_labels), outbound (send_message, reply_to_message, forward_message), HITL review (list_reviews, get_review, approve_review, reject_review), plus agent/domain/webhook management. Inbound is consumed by polling (list_messages) or a create_webhook subscription.

The hosted server is the primary path; npm publishing of @e2a/mcp-server is retired (frozen at 0.5.0). See mcp/README.md for per-framework setup and the full tool reference.

CLI

npm install -g @e2a/cli
e2a login

The CLI covers both scripting (send/reply/messages/whoami, with a stable exit-code contract) and account management (agents, keys, protection). Drive agents interactively over the MCP tools or the SDKs instead; manage domains/webhooks in the web dashboard.

When the --forward <url> endpoint path ends in /v1/responses, listen switches to OpenAI Responses API forwarding: each inbound email is formatted as a Responses payload and the model's output is sent back as an auto-reply. Add --forward-token <token> to attach a bearer token to the forwarded request:

e2a listen --forward http://localhost:18789/v1/responses --forward-token <token>

See cli/README.md for full reference.

SDKs

Python

pip install e2a            # webhook mode
pip install 'e2a[ws]'      # adds WebSocket support

from e2a.v1 import AsyncE2AClient, construct_event

client = AsyncE2AClient()                                       # reads E2A_API_KEY
event = construct_event(request_body, signature_header, webhook_secret)  # parse + HMAC-verify
if event.type == "email.received":
    email = await client.inbound.from_event(event)
    print(email.envelope_from, email.verified, email.reply_targets)
    result = await email.reply({"text": "Got it!"})
    if result.status == "pending_review":
        print("awaiting approval", result.message_id)

WebSocket (no public URL needed):

from e2a.v1 import AsyncE2AClient

async with AsyncE2AClient(api_key="e2a_…") as client:
    async for event in client.listen("bot@your-domain.com"):
        if event.type != "email.received":
            continue  # tolerate future event kinds
        email = await client.inbound.from_event(event)
        result = await email.reply({"text": "Got it!"})
        if result.status == "pending_review":
            print("awaiting approval", result.message_id)

See sdks/python/README.md.

TypeScript

npm install @e2a/sdk

See sdks/typescript/README.md.

Deployment

Three audiences each configure a different surface:

The Go binary runs on any container host; storage is plain Postgres 14+; outbound mail goes through standard SMTP. Most workers coordinate via SELECT … FOR UPDATE SKIP LOCKED, so multi-replica is safe — the two real horizontal-scaling caveats are in-memory WebSocket fan-out and per-process rate limits.

See docs/deployment.md for the full env-var reference, shared-domain DNS setup, and scaling/limitation notes.

Security

• Identity — agent registration requires DNS TXT verification of domain ownership (custom domains)
• Domain auth — SPF and DKIM checked on every inbound message
• Header signatures — HMAC-SHA256 over the <t>.<body> signing string delivered in the X-E2A-Signature header; receivers reject timestamps older than 5 minutes
• SSRF protection — webhook URLs must be HTTPS (in production), resolve to public IPs, use domain names (no raw IPs, no private/loopback ranges)
• OAuth CSRF — single-use, time-limited nonce in the state parameter
• Production mode (env: production in config.yaml) enforces the above where development mode is more permissive

Report security issues privately — see SECURITY.md for the disclosure process and what's in scope. Do not file public GitHub issues for vulnerabilities.

Data handling

Live inbound and outbound message data is retained indefinitely; soft-deleted messages and inboxes are purged after 30 days by default. Outbound bodies and attachments remain retained through terminal review and delivery transitions. API keys are stored as hashes; attachments go in JSONB rows (no S3/GCS). Application logs include sender/recipient addresses (standard MTA practice) but never bodies, attachments, raw keys, or HMAC secrets. Users can self-export (GET /v1/account/export) and self-delete (DELETE /v1/account?confirm=DELETE — a restorable trash by default, permanent=true to erase at once) for GDPR Art. 15 / Art. 17 / CCPA.

See docs/data-handling.md for the full retention table, log fields, user-rights endpoints, and the operator-side responsibilities (backups, TLS, at-rest encryption, log redaction, compliance).

FAQ

Why not just use SendGrid / Resend / Postmark for sending and their inbound parsing for receiving?

Four things that aren't possible to bolt on without significant rework:

1. Inbound with no public URL. Agents authenticate with their API key and consume inbound mail over a WebSocket to /v1/agents/{email}/ws, by polling the REST API, or through the MCP tools — no webhook URL, no ngrok, no port forward. Useful for agents on developer laptops, edge devices, or behind corporate firewalls. SendGrid/Resend are webhook-only by design.

2. Email threading on every reply. e2a resolves the RFC Message-ID / In-Reply-To / References graph within each agent mailbox, emits correct reply headers, and keeps a server-owned topology identity for message reads. conversation_id remains independent application correlation. SendGrid/Resend never see inbound mail—they are not receivers—so they cannot provide this bidirectional mailbox-local topology without you building the receiving side yourself.

3. Slug provisioning on a shared domain. Operators set shared_domain: agents.e2a.dev and users POST {"email": "my-agent@agents.e2a.dev"} to immediately register an agent on the shared domain with no DNS configuration. Possible because e2a is the SMTP relay claiming the domain — Resend / SendGrid are providers, not platforms, and can't multi-tenant a shared address space without you running the relay yourself.

4. Built-in review hold + auto-expiration. A per-agent protection policy (outbound gate action review, or the content scan) holds mail in pending_review state. Reviewers approve via dashboard, magic-link email, the MCP tools, or the API; a background worker auto-acts on expired holds based on the holds.on_expiry config. Magic-link tokens are HMAC-encoded — stateless, no session backend. With Resend / SendGrid you'd hold the message in your own DB, build the timer, the approval UI, and the stateless review tokens.

You can absolutely use SES / Resend / SendGrid as e2a's outbound SMTP for delivery to humans — that's what outbound_smtp in config.yaml is for. They complement e2a; they don't replace the inbound receiver, agent abstraction, or any of the layers above transport.

Why email at all? Why not webhooks, gRPC, or MCP between agents?

Email is the only protocol where every human already has an address and a working client. Webhooks / gRPC / MCP are great inside systems you control, but they don't reach Gmail or Outlook. If you want an agent that talks to humans (or to other organizations' agents) without forcing everyone to install a new client, email is the universal substrate.

e2a doesn't replace webhooks or MCP — your agent receives email through them. It bridges email's universal addressability to the structured-data world the agent code already lives in.

What stops an attacker from spoofing authentication results?

The relay discards any sender-supplied authentication claims and evaluates SPF, DKIM, and DMARC itself. For webhooks, verify X-E2A-Signature with the subscription's whsec_ secret before trusting the structured result; a forged POST then fails verification regardless of its claimed DMARC status.

Receivers verify with the SDK — construct_event(body, header, secret) / constructEvent(body, header, secret) does parse + HMAC verify in one call (or verify_webhook_signature(...) / verifyWebhookSignature(...) if you only need the boolean check). No API call back to e2a needed. If a signing secret leaks, rotate it via the dashboard; the previous secret keeps verifying through a 24h grace window, then stops. If it is stolen from the relay itself, treat the relay as compromised rather than trusting any webhook headers it emits.

Isn't this just SMTP with extra steps?

Yes — and the extra steps are the point. Concretely:

• SPF/DKIM verdict normalization so receivers don't reimplement domain auth
• Structured SPF/DKIM/DMARC evidence with explicit identifier alignment
• WebSocket / REST / MCP transport for agents without public URLs
• HITL approval flow with auto-expiration and stateless magic-link review
• Mailbox-local reply topology plus caller-owned application correlation
• Slug-based agent provisioning on a shared domain
• Per-agent webhook routing, rate limits, and HITL config

Building those on top of bare Postfix is a real project. e2a is that project, open source.

How does this compare to running Postfix or Postal myself?

If you want a full MTA, run an MTA — Postfix and Postal are great. e2a isn't trying to replace them at the SMTP transport level (it uses go-smtp for receiving and dial-out for sending). The value is the layer above transport: the auth model, agent abstraction, signed delivery contract, retry policy for webhook failures, HITL approval flow, SDKs and CLI. If you're comfortable operating an MTA and only need email plumbing, e2a may be more than you want. If you want the agent abstraction and signed identity layer prebuilt, that's what this is.

Why open source if there's a hosted version?

Two reasons:

1. Auditability. Identity infrastructure for your agents should be readable code, not a vendor black box. You can verify the cosign signature on ghcr.io/tokencanopy/e2a, reproduce the build, and confirm what's actually running.
2. Self-host as a real option. The hosted instance at e2a.dev runs the same ghcr.io/tokencanopy/e2a image you can pull right now. Convenience features on the hosted side (the shared agents.e2a.dev domain, managed deliverability) are config + DNS, not closed-source extras.

The hosted version at e2a.dev has paid tiers (a free tier plus paid plans); billing is opt-in on the hosted side — config (settable via env) points the OSS server at an external limits/billing sidecar, and the OSS code path stays unchanged. Self-hosting runs on generous default limits with no billing.

Development

make build               # go build -o bin/e2a ./cmd/e2a
make run                 # build + run (cp config.example.yaml config.yaml first)
make test                # all Go tests (needs Postgres on :5433)
make test-unit           # Go unit tests only (no DB)
make test-integration    # integration tests (needs Postgres)
make test-e2e            # e2e tests (needs Postgres)
make cover-check         # tests + per-package coverage floors (needs Postgres)
docker compose up -d postgres mailpit  # local Postgres + Mailpit only
make migrate             # apply SQL migrations to local DB

See CLAUDE.md for the full developer guide (architecture, tests, code generation, conventions).

Self-host (Docker)

Requires Docker.

git clone https://github.com/tokencanopy/e2a.git
cd e2a
docker compose up -d

Postgres comes up first (migrations run automatically), then the API server, then the dashboard. Four host ports:

• :8080 — HTTP API
• :2525 — SMTP relay
• :3000 — Dashboard (Caddy + Next.js, proxies /api/* to the API server)
• :8765 — Local MCP HTTP endpoint (what claude mcp add expects)

Health check:

curl http://localhost:8080/api/health
# {"status":"ok"}

Open http://localhost:3000 in a browser to view the dashboard. Sign-in requires Google OAuth credentials configured in config.yaml; for an API-only smoke test you can skip the dashboard and use the bootstrap flow below.

Create your first user and API key (no OAuth required):

docker compose exec e2a e2a -config /etc/e2a/config.yaml -bootstrap-email you@example.com
# User:    you@example.com (id=...)
# API key: e2a_...

Save the key — it's only shown once. Register an agent and confirm it works:

KEY=e2a_...
curl -X POST http://localhost:8080/v1/agents \
  -H "Authorization: Bearer $KEY" -H "Content-Type: application/json" \
  -d '{"email":"my-bot@agents.localhost"}'   # the local compose shared domain (or a domain you've verified)

curl -H "Authorization: Bearer $KEY" http://localhost:8080/v1/agents

To receive real inbound mail, point a domain's MX record at your relay host:

• A: your-domain.com → server IP
• MX: your-domain.com → your-domain.com (priority 10)

Then register and verify the domain through the API (see Domains). Without DNS, the API still works for testing — but external email won't reach your relay.

Upgrades and migrations. The e2a binary embeds migrations/*.sql and auto-applies any pending ones at startup (tracked in a schema_migrations table). When you upgrade e2a, restarting the container applies new schema migrations automatically — no manual step. E2A_MIGRATION_MODE controls this: auto (default, applies pending), verify (refuse startup and report pending), or skip (emergency surgery). Migrations are idempotent and non-destructive, so re-applying is safe.

Thread-identity upgrades include several CREATE INDEX CONCURRENTLY migrations. The direction-aware legacy-anchor indexes inspect existing message rows and can keep the first upgraded process in migration startup until each build completes; schedule the rollout with normal migration headroom and monitor startup logs. They take the migration advisory lock but do not block ordinary reads or writes.

(The compose file also mounts migrations/ into Postgres' init directory, but that path only runs on first start with an empty data volume — the binary's startup auto-apply is what keeps an upgraded deployment current.)

Contributing

By submitting a pull request, you certify the Developer Certificate of Origin for your contribution. Sign your commits with git commit -s.

License

Apache 2.0 — see LICENSE and NOTICE.