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Transactional email, stamped and accounted for.

One HTTP request sends your app's password resets, receipts and alerts. Every project sends in isolation, and every event reaches you signed. From €9 a month.

  • No card needed to test
  • Prices in euros, excluding VAT
curl -X POST https://api.outstamp.dev/v1/emails \
  -H "Authorization: Bearer $OUTSTAMP_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: welcome-42" \
  -d '{
    "from": "Acme <[email protected]>",
    "to": "[email protected]",
    "subject": "Welcome to Acme",
    "html": "<p>Your account is ready.</p>"
  }'

202 Accepted

{
    "id": "em_2n4k8x1q7c5m9r3t6v0w2y4a",
    "object": "email",
    "environment": "test",
    "status": "queued",
    "recipient_count": 1
}
  1. email.accepted0 ms
  2. email.queued64 ms
  3. email.sent0.8 s
  4. email.delivered2.3 s

From sign-up to delivered in three steps.

  1. 1

    Create a project

    It comes with its own isolated sending tenant, a test environment and an os_test_ key.

    Test key

    os_test_a1b2c3d4_••••••••

    Test
  2. 2

    Add your domain

    Copy the DKIM, MAIL FROM and DMARC records. We check them and tell you which one is missing.

    DNS records for send.acme.com
    CNAMEDKIMVerified
    CNAMEDKIMVerified
    CNAMEDKIMVerified
    MXMAIL FROMVerified
    TXTSPFVerified
    TXTDMARCRecommended
  3. 3

    Send with one request

    POST /v1/emails answers 202 with an email id once the email is safely stored.

    POST /v1/emails202

    em_2n4k8x1q7c5m9r3t6v0w2y4aqueued

The parts you would otherwise build yourself.

Every project starts with them switched on.

Test without emailing a real person.

Mail sent with a test key never leaves Outstamp. Send to a simulator address and get the exact event you asked for, webhooks included.

Simulator addresses and the event each one produces
Send toYou get
delivered@simulator.outstamp.devemail.delivered
bounce@simulator.outstamp.devemail.bounced
transient@simulator.outstamp.devemail.delivery_delayed
complaint@simulator.outstamp.devemail.complained
suppressed@simulator.outstamp.devemail.suppressed

Webhooks you can verify, retry and replay.

Every event is signed with HMAC-SHA256. A failed delivery is retried 10 times over 48 hours, and any event can be replayed for 30 days.

Outstamp-Id: whd_9r3t6v0w2y4a7c1e8g2j4l5n

Outstamp-Timestamp: 1789041600

Outstamp-Signature: v1=5d41402abc4b2a76b9719d91…

Delivery attempts over 48 hours

  1. 0s
  2. 5s
  3. 1m
  4. 5m
  5. 30m
  6. 2h
  7. 6h
  8. 12h
  9. 24h
  10. 48h

One project cannot sink another.

Each project sends from its own isolated tenant. If one project's bounce rate climbs, only that project slows down or pauses.

  • Acme app

    Bounce rate 0.4% in 24 hours

    Sending
  • Acme staging

    Bounce rate 0.1% in 24 hours

    Sending
  • Side project

    Bounce rate 5.2% in 24 hours

    Paused

Retry safely. Nothing goes out twice.

Repeat a request with the same Idempotency-Key and you get the first answer back, not a second email.

RequestIdempotency-Key: welcome-42202
RetryIdempotency-Key: welcome-42202 · replayed

One email sent.

What you pay at each volume.

Each provider's own public prices, side by side, in their own currency.

Monthly price of the cheapest plan, as listed on each pricing page, that covers each volume. Outstamp in euros excluding VAT; the others in US dollars as published, with no conversion. Checked on 30 October 2026.
Provider10,000/month50,000/month100,000/month500,000/month
Outstamp€9Starter€25Growth€39Pro€179Scale
ResendUS$20ProUS$20ProUS$35ProUS$350Scale
MailgunUS$15BasicUS$35FoundationUS$90ScaleNot shown
PostmarkUS$15BasicNot shownNot shownNot shown

Sources: resend.com/pricing, mailgun.com/pricing, postmarkapp.com/pricing. "Not shown" means the pricing page does not state a price for that volume in its text.

Prices in euros, excluding VAT.

A monthly plan, plus only the emails above what it includes. Testing is free.

Pricing details

Test

Build and test before you pay.

€0

  • Test keys, simulator and webhooks
  • Real emails to your own verified address
  • No card and no time limit
Start testing

Starter

€9/month

Billed monthly

  • 10,000 emails a month
  • Extra emails: €1 per 1,000
  • Test and live environments

Growth

€25/month

Billed monthly

  • 50,000 emails a month
  • Extra emails: €0.80 per 1,000
  • Test and live environments

Pro

€39/month

Billed monthly

  • 100,000 emails a month
  • Extra emails: €0.70 per 1,000
  • Test and live environments

Scale

€179/month

Billed monthly

  • 500,000 emails a month
  • Extra emails: €0.45 per 1,000
  • Test and live environments

Who you are dealing with.

  • Sent from the EU

    Your mail is sent from the European Union, from a tenant that belongs to your project alone.

  • Invoices from Portugal

    Invoices are issued in Portugal, with your VAT number on them.

  • Limits in the open

    Every limit, retry schedule and retention period is published in the public docs, so you can check them before you sign up.

  • A founder you can reach

    You talk to the person who builds Outstamp: @daminufe on X or df.pt.

Questions before you switch.

All questions
Will my emails land in spam?

Nobody can promise the inbox, and we don't. We set up what depends on us: DKIM, SPF, DMARC and MAIL FROM, checked automatically. And the events tell the truth: delivered means the recipient's server accepted the message.

Do I need to run any email infrastructure?

No. You never run mail servers or build the pipelines that process bounces and complaints. Outstamp runs them for every project.

Do I need a card to try it?

No. Test keys, the simulator and webhooks are free, and you can send real emails to your own verified address. You add a card when you start sending live.

What if I want to leave?

You are not locked in. The API is plain REST with no SDK to adopt, and your DNS stays yours. Moving to another provider means changing one HTTP call.

50% off for 12 months, for the first 10 teams.

We help you with DNS and the move. In return, we ask for an honest testimonial once you are happy.

  • No card needed to test
  • Prices in euros, excluding VAT