The email delivery
platform for teams
that actually ship.

Purpose-built for transactional and marketing email. Set up in minutes, scale to billions.

Join waitlist
Product Mockup

Design email layouts with total layout control.

Compose layouts with React or custom raw templates. Inject recipient fields, lists, and loops seamlessly and test live renders immediately.

welcome-email.tsx
TypeScript
import { Html, Button, Text } from "@react-email";
// Generate personalized client invoice
export default function InvoiceEmail({ name, amount }) {
return (
<Html>
<Text>
Hi {name}, your invoice for {amount} is ready.
</Text>
<Button href={`/invoice/${id}`}>
View Invoice
</Button>
</Html>
);
}
Live Render PreviewDynamic
To: Aryan Kapoor

Hi Aryan,

Your monthly subscription invoice for $29.00 is now ready. Click below to view details.

Route Blueprint
1

Your Application

API Payload

2

Letterstack SMTP Pool

US-East routed IP

3

Recipient Mailbox

Inbox placement

Live Delivery Logs
Active
12:04:01✓Request received from API
12:04:02✓Personalization compiler completed
12:04:02✓DKIM & SPF signature verified
12:04:03✓IP Pool assigned: transactional-us-east
12:04:04✓Delivered SMTP response (250 OK)
12:04:12✓Delivered to target mailbox inbox
12:04:28iWebhook payload sent to client
Deliverability Score

99.8

Excellent

Domain Reputation Safeguards

IP Address Health

Clean (0 Blocklists)

Active

SPF & DKIM Keys

Verified & Locked

Active

DMARC Configuration

Reject Policy Active

Active

Spam Report Rate

0.01% (Limit: 0.10%)

Active
Segment Conditions
WHENOpened Campaign
is welcome-onboarding
AND
WHENDomain Organization
is Y-Combinator company
Matching Users4 matched

Aryan Kapoor

aryan@superwall.com

Active

María González

maria@framer.com

Active

Tom Chen

tom@plane.so

Engaged

Sarah Kim

sarah@linear.app

Active
Hourly Open Performance
08:00 AM12:00 PM04:00 PM
Client Agent Distribution
Gmail app64.2%
Apple Mail22.8%
Outlook Client9.5%
Other Clients3.5%
Client API Setup
Node.jsPython
const letterstack = require("letterstack-node");
const client = new letterstack.Client({
apiKey: "ls_live_a1b2c3d4..."
});
client.emails.send({
from: "Aryan <aryan@superwall.com>",
to: "maria@framer.com",
subject: "Welcome to the stack 🚀"
});
Live Event Webhooks
Endpoint URL
https://api.framer.com/webhooks/emails
Subscribed Events
delivered
opened
clicked
bounced
Onboarding Flow Steps
Trigger: Account Signup
1d
Action: Wait 24 Hours
Action: Send Product Walkthrough
Journey Conversion Rate
Step 1 (Welcome Onboarding)96.8%
Step 2 (Product Walkthrough)78.4%

Letterstack replaces your entire email delivery stack.

Stop wiring together different services for marketing campaigns, transactional logs, bounce protection, and template designers. Letterstack does all of it, built on a single robust platform.

R

Simple two-step delivery

Draft your layout templates, assign your subscriber lists, and dispatch campaigns to millions of inboxes instantly.

To:Lucia GarzaJudah MontesRoselyn McCoy+3 more
Cc:Optional carbon copy list
Subj:Welcome to Letterstack
From:setup@letterstack.io

Hi {first_name},

We are building state-of-the-art web applications with React and TypeScript using industry best practices.

Get Started
Sender Hub
LG
Lucia Garza
Opened
JM
Judah Montes
Delivered
RM
Roselyn McCoy
Clicked
JH
Jett Higgins
Delivered
LC
Leighton Castillo
Opened
KV
Kai Villanueva
Delivered
Letterstack Founders

“We built Letterstack to give developers a single, robust API that handles email delivery, authentication, and inbox placement automatically.”

ER

Ethan Rodrigues

Co-Founder & CTO, Letterstack

“Instead of hacking together template engines, bounce monitors, and routing services, Letterstack manages your entire email delivery pipeline in one fast tool.”

KP

Krish Pinto

Co-Founder & CEO, Letterstack

Real email,

Real HTML, not a flattened imageOn
Vendor lock-inOff
Send from your own domainOn
Gmail clipping your layoutOff
Amazon SES pricing, no markupOn
Hidden per-seat feesOff
Bounce & suppression handlingOn
Manual list cleanupOff
Real HTML, not a flattened imageOn
Vendor lock-inOff
Send from your own domainOn
Gmail clipping your layoutOff
Amazon SES pricing, no markupOn
Hidden per-seat feesOff
Bounce & suppression handlingOn
Manual list cleanupOff
Real HTML, not a flattened imageOn
Vendor lock-inOff
Send from your own domainOn
Gmail clipping your layoutOff
Amazon SES pricing, no markupOn
Hidden per-seat feesOff
Bounce & suppression handlingOn
Manual list cleanupOff
Real HTML, not a flattened imageOn
Vendor lock-inOff
Send from your own domainOn
Gmail clipping your layoutOff
Amazon SES pricing, no markupOn
Hidden per-seat feesOff
Bounce & suppression handlingOn
Manual list cleanupOff

sent the way you actually built it.

No flattened screenshots, no clipped layouts, no per-seat pricing tricks — what you design is exactly what lands in the inbox, sent from a domain you own.