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Add email to your app in minutes.One key, one DNS record, done.

Sign-in codes, receipts, password links. One request and letr.dev delivers it. CHF 12 a month for 10'000 recipients.

Coming soonRead the docs

The simplest request

From, to, subject, text. The response is a 202 and an id you can follow in the dashboard or through the webhook.

Send your first email
POST /v1/emails
curl https://api.letr.dev/v1/emails \
  -H "Authorization: Bearer letr_..." \
  -H "Content-Type: application/json" \
  -d '{
    "from": "Acme <[email protected]>",
    "to": "[email protected]",
    "subject": "Your sign-in link",
    "text": "Sign in: https://acme.dev/l/7Fq2"
  }'

202 Accepted

{
  "id": "em_gk3lx0aqw2rz9vb7nc1ep4ty",
  "status": "queued"
}

What you can count on

Five promises. Each one is a thing you can look at in the dashboard, and a page where the rule is written down.

Live in minutes

Pay, add one DNS record, create a key, send. Or paste one prompt into your coding agent and it wires letr.dev into the project you already have.

Quickstart 
# everything letr.dev needs from you
letr._domainkey.mail.acme.dev
  TXT  v=DKIM1; k=rsa; p=MIIC…
POST https://api.letr.dev/v1/emails

Your mail keeps going

Past 10'000 a month, sending continues at CHF 0.50 per started 1'000, up to the ceiling you set. Emails at 80 % and 100 % of the plan, and at 90 % of the ceiling.

Plan and ceilings
11'340sent this month, 10'000 included
1'340 over, CHF 1.00 so far. Sending continues up to the ceiling you set.Marks: an email at 8'000 (80 %), at 10'000 and at 22'500 (90 % of the 25'000 ceiling).

No silent suspension

The pause thresholds are public: 5 % bounces, or 0.3 % complaints with at least 2, over 7 days. The dashboard shows how far you are from them.

Every limit and status code
Bounces
0.8 % of 5 %
Complaints
0 of 0.3 %
Last 7 days, 2'610 sent. The orange line is where an account pauses. Nothing pauses before 50 recipients in the window.

You see everything

30 days of messages and events, a signed webhook for every delivery, bounce and complaint, metrics by day and domain.

Webhook guide

A person answers

First answer within 1 Swiss business day; a stopped or paused account within 4 business hours.

Support terms

letr.devYour account is paused: 5.4 % bounces over the last 7 days, 2'610 sent. 141 of them went to addresses on one list imported on 28.10.

letr.dev supportWe have resumed the account. The 141 addresses are on your suppression list now; sending to the rest continues. Reply here if the list was intentional.

How you start

1

Pay, and you are live

CHF 12 a month. Live the moment the payment is confirmed; a person reads your sign-up afterwards.

2

Add your domain, create a key

One DNS record per domain. A key for sending, reading or both, limited to one domain if you want.

3

Send, and the limit grows

50 recipients a day to begin with. 500 once we have reviewed your account and you have 3 clean days and 200 delivered recipients behind you, 2'000 after 2 more weeks and 2'000 delivered, no daily limit from your first renewal.

Limits and the trust ladder

One plan

CHF 12a month

10'000 recipients includedCHF 0.50 per started 1'000 over cancel monthly
Coming soon
  • For companies and private persons
  • Past 10'000 your mail keeps going, up to the ceiling you set: 10'000 or 25'000 a month
  • Emails at 80 % and 100 % of the plan and at 90 % of the ceiling
  • A person reads your sign-up after you are live. If we decline it: full refund, with the reason

For developers

API reference

Every endpoint with parameters, schemas, responses and code samples.

Open the reference

Webhooks

Standard Webhooks signatures with Node and Python examples, retries and mutual TLS.

Webhook guide

API keys and permissions

Sending, read-only and full access, keys limited to one domain, rolling without downtime.

Key guide

MCP server

Claude, ChatGPT, Cursor and other MCP clients, with the same rules as the API.

Connect a client

SMTP

smtp.letr.dev for tools that only speak SMTP, with an API key as the password.

SMTP guide

Status page

Health of the API and the mail pipeline, measured by Starwatch.

status.letr.dev

Start sending today

CHF 12 a month, cancel monthly, live the moment the payment is confirmed.

Coming soon
[email protected]

First answer within 1 Swiss business day. A stopped or paused account within 4 business hours.

HeadquartersViascom GmbHWeissbadstrasse 8b
9050 Appenzell
Switzerland