Questions and answers

What is letr.dev?

letr.dev is a transactional email API from Viascom GmbH in Switzerland. Your application sends sign-in codes, receipts, password links and other one-to-one emails through one HTTPS request, through SMTP or through the hosted MCP server. letr.dev delivers them and reports every delivery event back through signed webhooks and the dashboard.

What does it cost?

CHF 12 a month for 10'000 recipients, tax added at checkout where it applies. Past 10'000, sending continues at CHF 0.50 per started 1'000 recipients, up to a monthly ceiling you choose: 10'000 or 25'000. You cancel monthly, effective at the end of the paid period.

How many emails can I send on the first day?

50 recipients a day to begin with. The limit grows with a clean sending record: 500 once letr.dev has reviewed your account and you have 3 days and 200 delivered recipients behind you, 2'000 after 2 more weeks and 2'000 delivered recipients, and no daily limit from your first renewal. The monthly ceiling applies throughout. Limits has the table.

Can I send newsletters or campaigns?

No. letr.dev sends transactional email only: messages your application sends to one person because of something that person did. No newsletters, campaigns, bulk or cold email, and no open or click tracking.

When does letr.dev pause an account?

At a bounce rate of 5 %, or at a complaint rate of 0.3 % with at least 2 complaints, each measured over the last 7 days and counted once the account has sent to 50 recipients in that window. A failed payment for the plan pauses the account too. The dashboard shows the reason, an account.paused webhook event carries it, and a person answers within 4 business hours.

Where is my data?

Email content and message logs are stored and processed on letr.dev's servers in Germany (Hetzner), with encrypted database backups at Contabo in the EU; Viascom GmbH in Switzerland operates letr.dev. Content is kept encrypted with the email for as long as the email is in your history (30 days, 365 with the add-on) and deleted with it; a recipient erasure deletes the content of every email addressed to the erased recipient or naming it in its subject or tags at once. A scheduled email that only names the address in its subject or tags is still sent at its time, and letr.dev's queue keeps it until then. Sender, recipients, subject, tags and delivery events are shown for 30 days and deleted after 32; with the 365-day history add-on they are shown for 365 days and deleted after 367. The privacy policy and the reliability guide have the details.

Can I see what letr.dev sent?

Yes. The email's page in the dashboard and GET /v1/emails/{id}/content show the content of each email, attachments included, for as long as the email is in your history: 30 days, or 365 with the history add-on. A recipient erasure deletes the content of every email addressed to that recipient or naming it in its subject or tags at once. A scheduled email that only names the address in its subject or tags is still sent at its time, and letr.dev's queue keeps it until then.

Does Viascom read my emails?

Not to operate the service. On suspicion of a breach of the Acceptable Use Policy, an operator may open the content of an individual email; each access needs a written reason, is recorded in the account history letr.dev keeps, and you see its time on the email.

How do I send?

Three ways, with the same rules and limits: the HTTPS API (POST /v1/emails with a letr_ API key as a Bearer token), SMTP at smtp.letr.dev on port 465 or 587 with letr as the username and an API key as the password, or the hosted MCP server for assistants such as Claude, ChatGPT and Cursor. The quickstart sends the first email in a few minutes.

Is there a free plan or a trial?

No. You pay the first month and are live the moment the payment is confirmed, starting at 50 recipients a day. The test addresses under test.letr.dev let you check an integration without delivering mail. Cancel monthly.