How can Letterhead integrate with other software?

Letterhead connects to other software in three main ways, from no-code to fully custom:

1. Zapier — no code required
2. API — requires a developer
3. Webhooks — may require a developer

Letterhead also ships built-in integrations that need no code at all — ESP sending through Iterable or Mailchimp, CRM audience sync (HubSpot and Mailchimp), Stripe, Slack notifications, the WordPress plugin, and an MCP server for AI tools. See Working in Integrations for the full list.

Zapier

This is the no-code option for connecting Letterhead to other applications.

You’ll need a Zapier account (free or paid), and the application you want to connect must already integrate with Zapier.

Zapier is a no-code automation platform that connects apps to automate workflows. You create automated sequences, called “Zaps”, that trigger actions based on events in one app and execute tasks in another — without any coding.

How Zapier works

• Trigger — an event in one app starts the workflow (e.g., a newsletter goes out from Letterhead).
• Action — Zapier performs an action in another app based on the trigger (e.g., sends a Slack message letting your team know it went out).
• Multi-step Zaps — chain multiple actions together.

Use cases

• Add or update contacts and manage tags
• Add an article to Curations
• Send a Slack message when a newsletter is published

See Letterhead + Zapier to get connected.

API

APIs let developers sync data between platforms — for example, a new contact entered in your CRM auto-populating into Letterhead. It’s the most versatile option we offer.

This option requires a developer to build against our API documentation. To get started, you’ll need an API key from your Letterhead account — see Generate & manage API keys and Using the Letterhead API.

Use cases

• Add, update, or remove subscribers
• Add articles to your Curations library
• Schedule or send a letter based on an action in another application
• Retrieve analytics, such as audience overlap between newsletters

Webhooks

Webhooks are automated messages sent from an application whenever a specific event occurs — an event-driven complement to APIs. Where an API must be asked to pull or modify data, a webhook automatically sends data in response to an event, with no request needed. Webhooks only send information, so they’re more limited than the full API.

When an event happens in Letterhead — such as a newsletter going out — a webhook lets the other application know so it can trigger its own action.

This option may require a developer. That said, if you use a third-party automation tool with webhook actions — like Workato or Integrately — you can use Letterhead webhooks without deep technical expertise.

See How can I use webhooks with Letterhead? for setup.

Use cases

• Updating a contact’s subscription status in your CRM when they unsubscribe in Letterhead
• Notifying an advertiser by email when the newsletter is published
• Reacting when a promotion campaign changes

Need help?

Contact support and we’ll help you pick the right option.