# Sendly for developers — one API for transactional email > The Sendly developer platform: one REST API for transactional email, idempotent sends, webhooks, an event stream, typed SDKs, and MCP access for AI agents. Canonical page: https://sendly.now/developers For developers · REST API + SDKs # Send email with _one_ API call. A REST API designed by people who have to use it. Idempotency keys, tagged sends, full event streams, and SDKs that look like the docs. [Read the docs →](https://docs.sendly.now)[Get API key](https://app.sendly.now/auth/signup) 1curl 'https://api.sendly.now/api/emails' \ 2 -X POST \ 3 -H "Authorization: Bearer sk_live_…" \ 4 -H "Idempotency-Key: ord_8f2a1c" \ 5 -H "Content-Type: application/json" \ 6 -d '{ 7 "from": { "name": "Acme", "email": "hello@acme.com" }, 8 "to": "jane@example.com", 9 "subject": "Welcome to Acme, Jane.", 10 "body": "

Your account is ready.

", 11 "tags": ["onboarding", "welcome"] 12 }' 1import { Sendly } from 'sendly-sdk' 2 3const sendly = new Sendly(process.env.SENDLY_KEY) 4 5await sendly.emails.send({ 6 from: 'Acme ', 7 to: 'jane@example.com', 8 subject: 'Welcome to Acme, Jane.', 9 html: '

Your account is ready.

', 10 tags: ['onboarding', 'welcome'], 11 idempotencyKey: 'ord_8f2a1c', 12}) 1from sendly import Sendly 2 3sendly = Sendly(key=os.environ['SENDLY_KEY']) 4 5sendly.emails.send( 6 from_='Acme ', 7 to='jane@example.com', 8 subject='Welcome to Acme, Jane.', 9 html='

Your account is ready.

', 10 tags=['onboarding', 'welcome'], 11 idempotency_key='ord_8f2a1c', 12) 200 OK·142 ms·fra-1 { "id": "msg\_8f2a1c4b9d", "status": "queued", "to": "jane@example.com", "tags": \["onboarding", "welcome"\], "created\_at": "2026-05-24T14:32:09Z" } § 02First-class DX ## Built to send at _scale._ A REST API with idempotency keys baked in, queued by region, retried with exponential backoff, and signed webhooks for every event. Nothing falls on the floor. ▸ 200 OKmsg\_8f2a1c4b9djane@example.com128 ms ▸ 200 OKmsg\_8f2a1c4b9enoah@acme.io141 ms ▸ 200 OKmsg\_8f2a1c4b9fsam@hometeam.dev132 ms ▸ 200 OKmsg\_8f2a1c4ba0priya@studio.co119 ms ▸ 200 OKmsg\_8f2a1c4ba1leo@minor.app148 ms ▸ 200 OKmsg\_8f2a1c4ba2mira@orbit.so137 ms § 03Webhooks ## Every event, _as it happens._ HMAC-signed payloads, automatic retries with exponential backoff, dead-letter inspection. Server-Sent Events too if you'd rather stream straight to your dashboard. [Webhook docs →](https://docs.sendly.now/guides/webhooks) TimeEventRecipientLat 14:32:09Deliveredjane@example.com · msg\_8f2a1c142 ms 14:32:14Openedjane@example.com · gmail · iOS5.1 s 14:32:31Clickedjane@example.com · acme.com/setup22 s 14:32:40Deliverednoah@acme.io · msg\_8f2a1c4ba0141 ms 14:32:41Bouncedold@archive.dev · hard · suppressed98 ms 14:32:55Openednoah@acme.io · outlook · macOS14.8 s { "type": "email.delivered", "id": "evt_3d9c2b", "created_at": "2026-05-24T14:32:09Z", "data": { "email_id": "msg_8f2a1c4b9d", "to": "jane@example.com", "tags": ["onboarding", "welcome"], "latency_ms": 142 } } § 04Templates ## Write emails in _React._ First-class React Email support. Components, props, themes — the same toolchain you already use, rendered to inbox-perfect HTML on send. 1// emails/welcome.tsx 2import { Html, Heading, Text, Button } from '@react-email/components' 3 4export default function Welcome({ name, url }) { 5 return ( 6 7 Welcome to Acme, {name}. 8 Your account is ready. Here's what 9 to do next… 10 11 12 ) 13} 14 15Sent via sendly.emails.send({ react: }) § 05Broadcasts ## Write, design, _send._ No code required. For the marketers on your team — a visual composer that produces the same React Email components your transactional pipeline already uses. FromAcme ToAudience: Active users · 24,180 contacts SubjectA new way to write to your customers. B I U H₁ H₂ ¶ ↗ ▦ ▤ ⌘ HERO IMAGE · 1200 × 600 ### A new way to write to your customers. This week, Sendly ships a visual composer alongside the React Email pipeline you already know. Same components, same theme tokens — now with a drag handle. Designed for the marketers on your team. Reviewed by the engineers who own the codebase. Read the announcement → Styles HeadlineNewsreader BodyManrope · 15 Line height1.55 Colors Palette Spacing Block ↑24 Block ↓24 Inline12 § 06Audiences ## One contact, _complete_ history. Every send, open, click and bounce attached to a single record. Build live segments on any property — they update the moment a contact changes. Active founders tag\="founders" AND opened\_count\>5 AND last\_seen\>30d ago Live count4,218 § 07Deliverability ## Reach inboxes, _not spam._ DKIM, SPF and DMARC records generated for every domain you add. Continuous reputation monitoring, automatic suppression lists. Inbox-first Reputation Sending reputation tracked against Google Postmaster, Microsoft SNDS, and a panel of seed addresses — surfaced in your dashboard, not buried in a vendor portal. Auto-suppress Bounces & complaints Hard bounces and complaints automatically suppress, never charged, never retried. Manual override is one click away. TypeRecordTTLStatus CNAMEsendly.\_domainkey.acme.com3600Verified TXTacme.com → v=spf1 include:sendly…3600Verified TXT\_dmarc.acme.com → v=DMARC1; p=…3600Verified CNAMEbounces.acme.com3600Verified CNAMEtrack.acme.com3600Verified § 08Platform Features ## Everything in _your_ control. Analytics Intuitive analytics. Sent, delivered, opened, clicked — bucketed per domain, per tag, per template, with daily and hourly resolution. Logs Detailed logs. Every API call, every webhook delivery, every retry attempt — searchable by message ID, tag, or recipient. 200 POST /emails · msg\_8f2a1c · 142ms 200 POST /emails · msg\_8f2a1d · 138ms 429 POST /emails · rate\_limit · 12ms 200 POST /emails · msg\_8f2a1f · 156ms 200 GET /emails · 6 items · 24ms Access Scoped API keys. Issue keys per environment, per domain, or sending-only. Hashed at rest, revocable in one click. sk\_live\_prod\_••••2a1cFULL sk\_live\_send\_••••8b42SEND sk\_live\_eu\_••••f193DOMAIN Domains Domain auth, in one click. Add a domain, copy four DNS records, and Sendly verifies in the background. Multi-region SES included. ●acme.comVERIFIED ●mail.acme.euVERIFIED ●tx.acme.coPENDING Teams Team management. Invite by email, assign owner / admin / member roles. amin@sendly.nowOwner jane@acme.comAdmin noah@acme.ioMember \+ 3 moreMember Limits Rate limits, visible. Per-key request budgets surfaced live. No silent throttling — you see the meter before SES does. Today · 68,402 / 100,00068% Burst · 87 / 200 rps44% § 09SDKs ## Your stack, _first-class_ support. Hand-written SDKs that mirror the docs verbatim. Type-safe end to end. Versioned in lockstep with the API. Node.jsv0.2.0 · ESM + CJS $ npm install sendly-sdk import { Sendly } from 'sendly-sdk' const sendly = new Sendly(process.env.SENDLY_KEY) await sendly.emails.send({ from: 'Acme ', to: 'jane@example.com', subject: 'Welcome.', react: }) Pythonv0.1.0 · py 3.10+ $ pip install sendly-python from sendly import Sendly sendly = Sendly(key=os.environ['SENDLY_KEY']) sendly.emails.send( from_='Acme ', to='jane@example.com', subject='Welcome.', html=render(welcome, name='Jane'), ) Or keep the SDK you already run — Sendly speaks the transactional-send APIs of Resend, SendGrid, Postmark, Mailgun, and Plunk. Swap the base URL and the key. [Migration guides](https://docs.sendly.now/migrate) § 10Quick start ## Three lines. _One inbox._ Install the SDK, paste your API key, send. The dev-mode CLI watches your templates and renders live previews so you ship intentionally, not anxiously. [Read the quickstart →](https://docs.sendly.now)[Open API reference](https://docs.sendly.now/api-reference/overview) § 11MCP ## An endpoint for _agents._ Sendly runs a remote Model Context Protocol server, so an AI client can work in your account directly. You choose what it may do: permissions that cannot be undone — sending mail, revoking API keys — are never granted by default. They sit unchecked behind a warning, and you tick them yourself. ConnectSTREAMABLE HTTP Sign in with OAuth `claude mcp add --transport http sendly https://app.sendly.now/api/mcp` Or hand it a secret key `claude mcp add --transport http sendly https://app.sendly.now/api/mcp \ --header "Authorization: Bearer sk_…"` OAuth suits a person connecting a desktop client — you approve the permissions on a consent screen. A secret key suits a headless or CI agent, where the key’s own permissions are what the agent may do. Sending-only `pk_` keys are refused. What you can grantPICK PER CONNECTION Read your account Domains, mailboxes, contacts, templates, campaigns, analytics, usage Manage contacts & segments Create, update, delete, and re-segment your audience Manage templates & domains Draft templates, add sending domains, run guided DNS setup Build campaigns & webhooks Campaign drafts, webhook endpoints, custom events Send yourself a test email Prove sending works from the sandbox. Reaches your own address and no one else Send emailNeeds approval One-off sends, and mailing a campaign to its whole audience Run automationsNeeds approval Edit and enable workflows that keep sending on their own Create & delete mailboxesNeeds approval Provision inboxes on a verified domain — deleting one erases every message it holds Account administrationNeeds approval Create, rotate and revoke API keys, create projects, edit your suppression list An agent only sees the tools its grant covers — the rest are never registered. Withdraw a permission from Settings and the agent is refused on its next call. [Read the MCP guide →](https://docs.sendly.now/guides/mcp) [Add to Claude](https://claude.ai/directory/e2cba79c-6e59-4784-af25-93ce631ad368 "Add Sendly to Claude") [Claude Code](https://docs.sendly.now/agent-setup/claude-code "Claude Code")[Codex](https://docs.sendly.now/agent-setup/codex "Codex")[Cursor](https://docs.sendly.now/agent-setup/cursor "Cursor")[OpenCode](https://docs.sendly.now/agent-setup/opencode "OpenCode") ## Stamp something _today._ A free API key, three lines of code, and your first message lands in seconds. No card, no overage email, no surprises. [Get your API key →](https://app.sendly.now/auth/signup)[Read the docs](https://docs.sendly.now)