HubSpot
Bring recipients in from HubSpot.
Plugs into your stack
LetterCircuit is a physical-mail API for the AI era: send letters the same way you send any other automated action.
Salesforce
Bring recipients in from Salesforce.
Zapier
Bring recipients in through Zapier.
REST API
Send recipients to LetterCircuit through the REST API.
Webhooks
Webhooks for status, so you see status at every step.
MCP
MCP for AI agents.
CSV upload
Upload a recipient CSV.
Ready to send something real?
Get early access to LetterCircuit and see the whole workflow, from your list to a proof you approve to mail in hand.