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Transactional email and one-time codes, one API

One token. Two sends. The message departs.

One API for transactional email and one-time codes: the same token, the same events, the same place to look when you need to know what happened.

Start for free See pricing

No credit card · 200 emails a day, free for 100 days

The products

Three products. One account.

Each one answers a different need and is bought separately. What they share is the part that usually costs you time: one way to authenticate, one statement, and one place to look when something does not arrive.

Quathos Mailer

Your software sends email, and it arrives.

  • POST /v1/email/messages, with the message id already in the response.
  • Accepts the envelope of SendGrid’s POST /v3/mail/send.
  • Or the SMTP relay on port 587, if your stack already speaks SMTP.
See Quathos Mailer

One token for all three

The same authentication, the same webhook events, the same invoice. Adding a channel is not onboarding another vendor: it is calling another endpoint with the token you already have.

The Quathos Mailer doors (API, SendGrid compatibility and SMTP relay) converging into a single account.Quathos Mailerwhat your software sendsAPISendGrid compatSMTP relayQuathos Mailer

Why Quathos Mailer

Built for the send you have to explain later

Verify a sender, create a scoped token, POST. Everything after that is recorded, message by message.

One clean API

REST with a bearer token. The response carries the message id: the same id every event refers back to.

Authenticated from day one

SPF, DKIM, DMARC and forward-confirmed reverse DNS, on our own MTA. Bounces and complaints come back as events, not mysteries.

Predictable cost

Monthly plans by volume, in USD. The free tier is 200 emails a day, for 100 days, no card.

Real-time webhooks

Delivered, opened, clicked, bounced: signed, retried, and carrying your metadata back.

Verified senders

Confirm a single address, or authenticate the whole domain with four DNS records, your SPF untouched.

Secure & LGPD-ready

Scoped API tokens, tenant isolation, built-in opt-out and STOP handling: LGPD compliance without the legwork.

Sent is not the same as delivered

Authentication and reputation decide where your email lands. We handle both, and tell you which one it was.

Your app
Quathos Mailer API POST /v1/emails
Accepted 202
Signed and queued
Authentication SPFDKIMDMARC
Reputation
Blocked
Spam
Inbox
Suppressed

Delivered to the inbox

Every outcome comes back as a webhook

SPF DKIM DMARC Reverse DNS (PTR)

Sent from our own MTA, with SPF, DKIM, DMARC and forward-confirmed reverse DNS all in place, so mailbox providers trust the source before they even read the message.

Real-time events

Know what happened to every message

The moment a message is delivered, opened, clicked, bounces or draws a complaint, the event is pushed to your endpoint: no polling, no guesswork.

  • EMAIL msg_01JQ4C…a7
    1. queued
    2. accepted
    3. delivered
  • OTP vrf_01JQ4C…c9
    1. sent
    2. delivered
    3. checked
Delivered Opened Clicked Bounced Complained

Signed and verifiable

Each delivery is signed, so your app can prove the event really came from us.

Retried until it lands

A failing endpoint is retried with backoff, so you never silently miss an event.

Analytics that add up

The same events power delivery, open and click rates in your dashboard.

From zero to sent in three steps

1

Verify your sender

Confirm an email address or authenticate your domain.

2

Create an API token

Generate a scoped token, or a 7-day test token to try it out.

3

Send

POST to the API and track delivery in real time.

Developer-first

An API you’ll actually enjoy

Copy, paste, send. Client libraries optional.

Get started
Send your first email with one request
curl https://api.mailer.quathos.com/api/v1/email/messages \
  -H "Authorization: Bearer qmx_live_•••" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "you@yourcompany.com",
    "to":   "user@example.com",
    "subject": "Welcome aboard",
    "html": "<h1>You are in.</h1>"
  }'
SendGrid → Quathos Mailer

Migrate from SendGrid: swap the base URL and the key.

Point your existing code at us: the /v3/mail/send payload you already send is accepted as-is. Bring your suppression list and templates with a read-only key, and you can be sending the same afternoon.

Start migrating free See what’s compatible

No credit card. 200 emails/day free for 100 days.

1

Point your code at us

Swap the base URL and the token. Our /v3/mail/send compatibility endpoint accepts the payload you already build, no rewrite.

2

Bring your suppression list

Paste a read-only API key from your old account. We import bounces, complaints, unsubscribes and blocks: the part that protects your reputation.

3

Bring your templates

Handlebars renders as-is: {{#if}}, {{#each}}, {{this.x}} and friends. Anything outside that subset arrives as a draft, never published half-converted.

Pricing

Email plans by volume: the quota is part of the plan

Start free with 200 emails a day for 100 days. Move up only when you need more volume, or pay as you go from $0.28 per 1,000 emails with no subscription. No contracts, cancel anytime.

Free

For trying Quathos Mailer out

Free

200 emails / day

free for 100 days, then pick a plan

What's included

  • 1webhook endpoints
  • 60 req/minon the API
  • Dynamic templates + A/B testing
  • Delivery, open & click analytics
  • Automatic suppression management
  • 3 daysof log retention
  • Community support
Start for free

Starter

For small, steady sending

$12 /mo

50,000 emails / month

then $0.22 per 1,000 extra emails

What's included

  • 10webhook endpoints
  • 120 req/minon the API
  • Dynamic templates + A/B testing
  • Delivery, open & click analytics
  • Automatic suppression management
  • 30 daysof log retention
  • Email support
Choose Starter
Most popular

Growth

Best price per email

$29 /mo

150,000 emails / month

then $0.18 per 1,000 extra emails

What's included

  • 30webhook endpoints
  • 300 req/minon the API
  • Dynamic templates + A/B testing
  • Delivery, open & click analytics
  • Automatic suppression management
  • Add-onDedicated sending IP
  • 90 daysof log retention
  • Email support
Choose Growth

Scale

For high-volume senders

$69 /mo

500,000 emails / month

then $0.14 per 1,000 extra emails

What's included

  • Unlimitedwebhook endpoints
  • 600 req/minon the API
  • Dynamic templates + A/B testing
  • Delivery, open & click analytics
  • Automatic suppression management
  • Dedicated sending IP
  • 12 monthsof log retention
  • Priority support
Choose Scale

Enterprise

Custom volume with dedicated support

Custom

Let's tailor it to your volume

What's included

  • Unlimitedwebhook endpoints
  • Customon the API
  • Dynamic templates + A/B testing
  • Delivery, open & click analytics
  • Automatic suppression management
  • Dedicated sending IP
  • SSO / SAML
  • Customof log retention
  • Dedicated account manager

Talk to sales

Tell us about your volume and we'll tailor a plan for you.

More details (optional)

By sending, you agree to our privacy policy.

Prices in USD, billed monthly. Only email sends count toward your quota.

FAQ

Frequently asked questions

Everything you need to know before your first send. Still unsure? Talk to us.

What is Quathos Mailer?

One HTTP call sends the message; the event trail tells you what happened to it: delivered, opened, bounced, each pushed as a signed webhook. Verify a sender, create a scoped token, POST: welcome messages, receipts, one-time codes. Templates, per-tenant isolation and suppression handling are part of the same surface, not add-ons.

How fast can I start sending?

Minutes. Create an account, confirm a single sender address (or authenticate a whole domain), generate an API token, and POST your first message. No sales call, no credit card. Your trial gives you 200 emails a day for 100 days.

How does pricing work?

Simple monthly plans by volume, priced in USD. Every plan includes a monthly email quota that is already paid for by the subscription: sends inside your quota never touch your wallet. Only usage beyond the quota draws on prepaid credit. No hidden per-send fees, no surprise overages.

Do you handle deliverability and authentication?

Yes. Verifying a domain means publishing three CNAMEs and a DMARC record. Your existing SPF is never touched, and we never send from an unverified sender. Bounces and complaints come back as events, and suppressed addresses are honored on every send. Bounce and complaint rates are the two numbers reputation is built on; both are measured and visible per message.

How do webhooks and delivery events work?

Every message emits events: delivered, opened, clicked, bounced, complained, pushed to your endpoint in real time as they happen. Each delivery is signed and retried on failure, so you get an accurate, ordered picture of what reached your recipients without polling.

How are my API tokens and data kept secure?

Tokens are scoped and shown only once, at creation; we store a hash, never the full secret. Every tenant is isolated at the database level, marketing and transactional streams are separated from the schema up, and we never log passwords, codes or provider credentials.

Can I send marketing campaigns too?

Yes, with campaigns and contact lists in the dashboard, kept strictly separate from your transactional stream so promotional volume never contaminates the reputation of your critical mail. Opt-in, unsubscribe and STOP handling are built in.

Are you compliant with the LGPD?

We are built for it. Quathos Mailer acts as a data processor on your behalf: consent, opt-out and STOP are handled on every send, suppressed recipients are never messaged, and data retention is bounded by your plan. Every tenant is isolated at the database level and we never log message content, codes or credentials, so meeting the LGPD is the default, not extra work.

Coming from SendGrid? How do I migrate?

In one afternoon, usually. The dashboard has an importer: paste a read-only API key from your old account and bring your suppression list and templates. Handlebars templates ({{#if}}, {{#each}}) work as-is, no rewriting. Your code can stay too: our /v3/mail/send compatibility endpoint accepts the SendGrid payload, so switching is often just pointing the base URL and the token at us.

Start sending in minutes

Start free: 200 emails a day for 100 days. No credit card required.

Create your account