Mailstack

Your newsletter and your app's email, run from one terminal.

Mailstack sends both through Amazon SES. Write, test and send from the dashboard, the REST API, or your AI agent over MCP.

Get early access How sending stays clean

Open source, built on Cloudflare. In early access now.

Both kinds of email, one account.

The newsletter your readers signed up for, and the receipts and sign-in codes your app sends, share one domain setup, one suppression list and one log.

Newsletters

A hosted signup page, double opt-in, an editor with Markdown and HTML, test sends, scheduling and a report for every issue.

Sign up
jane@example.com
Subscribe
Confirm by email
Confirm
Get the issue

Transactional

Send one email or a batch with a request you already know, retried safely with an idempotency key, then follow each one by its id.

$ curl https://app.mailstack.ai/v1/emails \
    -H "Authorization: Bearer $MAILSTACK_KEY" \
    -H "Idempotency-Key: order-1042" \
    -d '{"from": "Acme <hello@mail.acme.com>",
         "to": "jane@example.com",
         "subject": "Your receipt", "html": "…"}'

{ "id": "em_01j9x4…" }

Only email people asked for.

Every workspace runs these checks, and they can't be turned off. Sending to people who didn't ask is hard, and it stops fast.

Before every campaign
  • Readers opted inSignups confirm by email first, and an import needs a statement of how those people agreed.
  • Unsubscribing takes one clickEvery email has List-Unsubscribe headers and a footer link, as Gmail and Yahoo require.
  • Bad addresses are skippedHard bounces and spam complaints join the suppression list and never get email again.
  • The domain is authenticatedDKIM, SPF through a custom MAIL FROM, and DMARC, on a domain the sender verified.
  • A postal address is in the footerCampaigns won't send without one, as anti-spam laws require.

Automatic pauses

Rates are counted over each sender's last seven days. Past these lines sending stops on its own, before it can affect anyone else.

Bounces Complaints
Paused over 2% over 0.08%
Blocked until reviewed over 5% over 0.3%

Bought, rented and scraped lists are banned by our acceptable use policy. Report abuse to hello@mailstack.ai.

Start with the email you already send.

Mailstack is in early access. Tell us what you send today, and we'll set you up.

Get early access