EMAIL API + AGENT OPERATIONS

Build the send.Delegate the rest.

One API for transactional, lifecycle, and campaign email. Your agent can configure domains, inspect failures, and prepare safe operations. You keep the keys and production authority.

Run the quickstart ↘ See the control plane ↓

Idempotent sends
Inspectable states
Signed webhooks

Linnet developer workspace with active email operations — 01
**The API returns fast. The ledger finishes the story.**Every state keeps its actor, reason, and timestamp.

POST /v1/emails202

{
  "id": "msg_01JQ8N…",
  "state": "accepted",
  "test_mode": true
}

The Linnet mail courier carrying a message

Agents do the busywork. Linnet keeps the rules. Humans keep authority.

FROM PAYLOAD TO INBOX

Change the message.
See what ships.

Start with the universal contract: one request, one rendered email, and one inspectable test-mode operation.

{
  "from": "Linnet <hello@linnetmail.com>",
  "to": "you@test.linnet.invalid",
  "subject": "Your workspace is ready",
  "stream": "transactional",
  "test_mode": true
}

POST /v1/emails202 · accepted

FromLinnet <hello@linnetmail.com>

SubjectYour workspace is ready

Linnet

WELCOME

You’re ready for the first send.

Your workspace is set up. Start in test mode, inspect the result, then decide when production is ready.

Open your workspace Sent through Linnet · test mode

WEBSITE TO EMAIL DESIGN SYSTEM

Your website becomes
a real email system.

Enter your website. Linnet reads its visual rules, drafts a complete email kit, and shows every decision before you approve it.

Not a recolored template.

Layout hierarchy, type roles, component shapes, border weight, shadows, and voice become reusable, email-safe rules.

Visual evidence attached
Desktop and mobile rendered
Agent-ready after approval

DESIGN COMPILER Whooshly system found

Website URL

Try , , or . Linnet reads the public CSS live; every detected choice remains editable.

WHOOSHLY / SAVED BRAND SYSTEM

Signal + stock palette
Space Grotesk + Arial
Square frame + offset shadow
Direct, signal-led voice

--email-card-radius: 0px;
--email-button-radius: 0px;
--email-border: 2px solid #17151d;

Brand name

Email job Accent color

Override the detected logoPNG, JPG, or WebP · processed locally

COMPILER OUTPUT

Source evidence attached
Components translated for email
Desktop and mobile checked
Waiting for your approval

FromWhooshly <hello@whooshly.co>

SubjectWelcome to Whooshly

WWhooshly

WELCOME

You’re in.

Thanks for joining Whooshly. Your account is ready whenever you are.

Open your account

BUTTON NOT WORKING?Copy and paste the secure link into your browser.https://whooshly.co/account/welcome

SIGNAL NOTEYour link and message state stay attached to this send.

Permission and message state stay attached in Linnet.

THE DEVELOPER CONTRACT

Send once.
Know what happened.

One request returns a stable Message ID. Policy decisions, attempts, retries, and recipient outcomes stay attached to it.

curl "$LINNET_API_URL/v1/emails" \
  -X POST \
  -H "Authorization: Bearer $LINNET_API_KEY" \
  -H "Idempotency-Key: welcome-018f" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "Product <hello@yourdomain.com>",
    "to": "person@example.com",
    "subject": "Your workspace is ready",
    "text": "Welcome aboard."
  }'

msg_01JQ8N…Delivered in 1.28s

09:41:02.104AcceptedIdempotency key stored
09:41:02.188Policy passedTransactional stream
09:41:02.401Provider acceptedattempt_03F…
09:41:03.384DeliveredSigned event verified

REST APITypeScript contractTest modeReplay-safe operationsProvider-neutral events

ONE EMAIL CONTROL PLANE

Your code and your agent read the same truth.

Transactional, lifecycle, and campaign email share identities, consent, delivery state, and evidence—without flattening their different safety rules.

One message ledger

Follow every request from intake to recipient outcome.

One operating contract

Humans, code, and agents act on explicit states.

No hidden authority

Agents prepare work; Linnet enforces the boundary.

Linnet deliverability workspace showing domain readiness — **No green tick without the evidence behind it.**Domain, policy, attempts, and outcomes stay readable.

DELIVER WITH EVIDENCE

Infrastructure that explains itself.

An agent can move quickly because the platform keeps every consequential boundary explicit.

01 / IDENTITY

Domain readiness

Ownership, DKIM, SPF, and DMARC remain visible facts—not a decorative green tick.

02 / SAFETY

Test mode

Exercise the request and event path without accidentally emailing real recipients.

03 / INTAKE

Idempotent sends

Repeat the same operation without creating a second Message.

04 / EVIDENCE

Durable message ledger

Acceptance, policy, attempts, and recipient outcomes stay on one record.

05 / EVENTS

Signed webhooks

Verify the exact event body and follow bounded retries when endpoints fail.

06 / AGENTS

Scoped credentials

Give an agent the narrow tools it needs without giving away human authority.

AGENT OPERATIONS

A tiny operations team.
Already knows the API.

Assign routine work without handing over production credentials or inventing a second control plane.

01 / ACCESSAPI locksmith

Scopes the key and keeps it out of the prompt.

02 / EVENTSWebhook electrician

Checks signatures and reconnects the handoff.

03 / RECOVERYLog detective

Finds the reason before anyone retries blindly.

THE HANDOFF IS THE PRODUCT

Agents get tools. Not root access.

Linnet checks identity, scope, state, policy, and freshness before any consequential operation moves.

AGENTPrepares

Inspects state and proposes an exact, replay-safe operation.

LINNETEnforces

Validates scope, policy, consent, freshness, and idempotency.

HUMANAuthorizes

Sets production boundaries and approves consequential changes.

OPERATION RECEIPTapproval_01JQ…

Actoragent:campaign-operator

Operationdomain.verify

Policypassed · v12

Authoritybounded tool grant

Change the operation and the approval expires. That is the point.

INSIDE THE CONTROL PLANE

Proof after the request.

Code gets a stable contract. Operators get the state needed to debug it without reconstructing the story from provider logs.

Linnet Message ledger with populated test activity — MESSAGE LEDGEREvery send becomes an inspectable record.

Linnet developer workspace with project keys, test send, and webhooks — DEVELOPER WORKSPACEKeys, test mode, and events in one place.

START WITH ONE REAL SEND

Let your agent do the email work.

Bring one use case. Validate the API, domain, and delivery trail in test mode before production traffic moves.

Build the send.Delegate the rest.

Change the message.
See what ships.

You’re ready for the first send.

Your website becomes
a real email system.

You’re in.

Send once.
Know what happened.

Give it the brief.
Review the exact send.

Your code and your agent read the same truth.

Infrastructure that explains itself.

Domain readiness

Test mode

Idempotent sends

Durable message ledger

Signed webhooks

Scoped credentials

Grow the relationship. Keep the evidence.

Explainable segments

Consent evidence

Frequency boundaries

Reusable email system

Frozen exact sends