Capture leads with forms, onboard and convert users with event-driven sequences, send broadcasts to any segment, and fire every transactional email. One integration, the whole lifecycle.
Turns out ducks are better at email than chimps.
Four building blocks on one contact list, one set of branded templates, and one sending pipe. No glue code between tools.
Capture Embeddable forms with double opt-in and spam protection turn site visitors into contacts, straight into Letter.
Explore forms →
Automate A visual canvas that fires on product events, form submissions, or list changes. Branch, wait, and convert.
Explore sequences →
Campaign One-off sends to a segment you build from traits, events, and lists, with a live audience preview before you ship.
Explore broadcasts →
Transactional Receipts, password resets, and notifications through one API call, the same templates, and the same deliverability.
Explore transactional →Drag and drop triggers, waits, conditions, and emails. Start from a product event, a form submission, or a contact entering a list, not vague “user attributes” pulled from a CRM.
From the first lead-capture form to the last transactional receipt, every message your product sends lives in one place.
Turn website visitors into subscribers, then warm them up.
Get new users to their first "aha".
Turn trials into paid, paid into upgrades.
Keep users active. Catch the ones drifting away.
Reach everyone at once, or just the segment that matters.
Every service email your product fires, one API call away.
No. Letter captures leads with embeddable forms (script, iframe, or plain HTML POST), confirms them with double opt-in, and drops them straight into the same contact database your product events feed. Capture, nurture, broadcast, and transactional all share one list, so there's no Zapier glue between a form tool and an email tool.
Userlist and Customer.io chase the same lifecycle-email outcomes, but they're built for product marketers wiring up sophisticated tooling. Letter targets the developer who actually has to plug it in: three API calls, a CLI, agent setup. Intercom is support chat with email bolted on; Kit (ConvertKit) is creator newsletters. Letter is email only, on purpose - marketing, lifecycle, and transactional in one pipe, nothing you'll never touch.
No. Letter handles delivery end-to-end: sending, deliverability, suppression, the lot. Connect a domain, we verify SPF/DKIM, and mail flies. If you'd rather send from your own verified domain, that's the default.
That's the plan. Transactional email - receipts, password resets, verification, notifications - is rolling out as the fourth pillar: one API call, the same branded templates and personalization as your marketing email, sent from your verified domain on the same deliverability infrastructure. Service messages correctly bypass marketing unsubscribe, and every send lands in the contact's timeline next to their lifecycle history.
Any unique person you've identified with Letter: a signed-up user, a lead from a form, a waitlist signup, anyone. We don't charge per event or per email, only per contact in your database.
No. The sequence canvas is drag-and-drop, but the email composer is a clean text editor that renders cross-client MJML under the hood, not a fiddly block builder. The dashboard shows engineers what shipped to whom, not conversion funnels you'd never look at twice. Letter is built for the people writing the emails, not the people pitching them.
Yes. Import contacts from CSV or directly via API. We can run alongside your existing tool during migration so nothing drops. We've written guides for the common ones.
Hand the one-liner to your coding agent, or drop the SDK in yourself. Identify users, track events, embed a form: sequences fire automatically. No webhooks to configure, no schemas to define.
npx @letterapp/cli One command wires Letter into your app. It opens your browser to confirm, provisions your key, and installs the SDK. Your key is never pasted into chat.
Free up to 1,000 contacts. No credit card. Drop the SDK in, fire your first event, watch it arrive.