Use mailbox.bot REST, MCP, and webhooks inside n8n to add approval-first postal mail to agentic or deterministic workflows.
n8n collects source data and creates the letter or PDF.
Agent or HTTP node calls mailbox.bot dry_run=true.
Approval branch confirms live send.
mailbox.bot sends mail and posts webhooks to n8n.
n8n updates the original app and continues the workflow.
curl -X POST https://mailbox.bot/api/v1/mail \ -H "Authorization: Bearer sk_agent_test_..." \ -H "X-Mailbox-MD-Version: 3" \ -H "X-Max-Cost-Cents: 1500" \ -F "document=@notice.pdf" \ -F "recipient_name=Recipient Name" \ -F "recipient_line1=123 Main Street" \ -F "recipient_city=San Francisco" \ -F "recipient_state=CA" \ -F "recipient_zip=94105" \ -F "mail_class=certified" \ -F "dry_run=true" \ -F 'metadata[source]=n8n'