Connect Letter to 6,000+ apps. Trigger Zaps when a contact is created or updated, and push contacts into Letter from anything Zapier touches.
Integrations
Plays nice with your stack.
Letter sits at the centre of your lifecycle, not off to the side. Pipe contacts and events in from the tools you already run, or wire up anything you like with the API, SDKs, and webhooks.
Pull leads from your Facebook lead forms straight into Letter and start a welcome sequence the moment they sign up.
Stream identified users and events from your Segment workspace so your campaigns fire on the data you already collect.
Sync people and product events from PostHog to trigger lifecycle emails off real in-product behaviour.
Automate workflows and route leads into Letter with Make scenarios, no code required.
Turn Tally form submissions into Letter contacts and kick off the right sequence automatically.
Don't see your tool?
Build it in minutes.
Letter is API-first. Identify a contact, track an event, or update a trait with a single call, then let sequences do the rest. When you'd rather react than poll, subscribe to webhooks and get pushed everything that happens.
REST API
Identify contacts, track events, and manage lists from any backend.
CLI
Bootstrap your integration with npx @letterapp/cli and wire up contacts in minutes.
Typed SDKs
Official libraries so you ship in a few lines, not a few days.
Webhooks
Subscribe once and get pushed every send, open, and conversion.
Ready when you are
One hub for
One hub for
every signal.
Free up to 1,000 contacts. No credit card. Connect a tool, fire an event, watch the sequence run.