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Connectors / Communication · HTTP Connector
Automate Lettr with Tray.ai
Send an email, create a campaign and create a contact in Lettr, and start a workflow when Lettr sends “Email delivered”.
What can you do with Lettr on Tray.ai?
Lettr is an email platform for developers that sends transactional emails and marketing campaigns, manages audience lists and templates, and tracks delivery and engagement. Tray.ai connects to Lettr through the HTTP Connector, so your workflows can call the Lettr API alongside the rest of your stack.
- Send an email with Lettr when a new user signs up in your app.
- When Lettr sends “Email bounced”, mark the contact's address as invalid in your CRM.
- When Lettr sends “List unsubscribe”, update the contact's preferences in your CRM.
- Create a contact in Lettr when a lead converts in your CRM.
- Connects through
- HTTP Connector
- Authentication
- A bearer token
- Base URL
- https://app.lettr.com/api
Set it up
Connect Lettr to Tray.ai
Each step uses Lettr's own API details, from its documentation.
Step 1
Save Lettr's API token
Save the token Lettr issues as a Tray.ai authentication. The HTTP Client sends it as a bearer token on every call. The token stays out of the workflow and out of the logs.
Step 2
Point the HTTP Client at the API
Add an HTTP Client step and use https://app.lettr.com/api as the base URL. Or paste a cURL example from Lettr's API docs, and Tray.ai fills in the method, URL, and headers.
Step 3
Start with “List email events”
It's one of 24 documented actions, under Emails. The response comes back as data the next step can map into your other apps.
Step 4
Start workflows from Lettr events
Give Lettr the URL of a Tray.ai webhook trigger. “Email delivered” can then start a workflow, and so can 6 other events.
Give your AI agents Lettr tools
Build an MCP server on Lettr in Agent Gateway and choose which actions your agents can call. Every call runs with access control and an audit trail. How Agent Gateway works
- Send an email
- Create a campaign
- List contacts
- List audience lists
- List templates
- List domains
- Schedule an email
- List email events
What the Lettr API covers
6 resources and 24 documented actions, each one a call the HTTP Connector can make from a Tray.ai workflow. Connecting it takes a few clicks: here's how.
Emails
- Send an email
- Schedule an email
- List email events
- Cancel a scheduled email
Campaigns
- Create a campaign
- List campaigns
- Send a campaign now
- Schedule a campaign
Contacts
- List contacts
- Create a contact
- Bulk create contacts
- Attach contacts to lists
Audience lists
- List audience lists
- Create an audience list
- Update an audience list
- Delete an audience list
Templates
- List templates
- Create a template
- Update a template
- Delete a template
Domains
- List domains
- Create a domain
- Verify a domain
- Delete a domain
Events Lettr can send to a Tray.ai webhook trigger
- Email delivered
- Email bounced
- Email delayed
- Spam complaint
- Email opened
- Link clicked
- List unsubscribe
Checked against Lettr's own documentation on 2026-10-22
How Tray.ai makes this work
Lettr plugs into the whole Tray.ai platform
Intelligent Integration
Integrate and automate across 10,000+ apps, databases, APIs, and services with visual workflows, error handling, and observability.
Learn more →Agent Builder
Build AI agents that read, write, and take action in Lettr — with guardrails, audit, and human-in-the-loop.
Learn more →Agent Gateway for MCP
Expose Lettr actions as governed MCP tools — observable, rate-limited, authenticated.
Learn more →Tray Helix
Build apps on Lettr data with your AI assistant, then deploy, run, and govern them on Tray.ai.
Learn more →More communication apps on Tray.ai
Dedicated connectors and other apps Tray.ai reaches in the same category. See every communication connector →
Frequently asked questions
What can a Tray.ai workflow do in Lettr?
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The Lettr API documents 24 actions across 6 resources (Emails, Campaigns, Contacts, Audience lists, Templates, Domains). For example: Send an email; Create a campaign; List contacts. A workflow can make any documented call through the HTTP Connector.
How does Tray.ai authenticate with Lettr?
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The Lettr API uses a bearer token. You save it once as a Tray.ai authentication, and the HTTP Connector adds it to every request.
Which Lettr events can start a Tray.ai workflow?
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Lettr sends 7 events to a webhook URL, for example: Email delivered; Email bounced; Email delayed; Spam complaint; Email opened; Link clicked; List unsubscribe. A Tray.ai webhook trigger receives them and starts a workflow.
See Lettr working against your stack.
We'll walk through a tailored demo with your systems plugged in.
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