Agentic mail
Send physical mail from an AI agent
An AI agent can send physical mail when the mailing system separates drafting from payment and execution. The safest default is for the agent to create a reviewable draft, return a PDF preview and checkout URL, and let the owner approve the final document, addresses, print options, delivery option, and price before the mailpiece is printed and posted.
Published Jun 20, 2026
Quick answer: how can an AI agent mail a real letter?
Use an MCP draft plus hosted checkout when a human can review payment. Use x402 or MPP only when the agent is running in an approved autonomous environment with a payment credential and spend controls.
| Agent goal | Best PostalForm path | Payment boundary | Real-world side effect |
|---|---|---|---|
| Draft a letter from text, HTML, Markdown, RTF, or PDF | Remote MCP draft tools | None yet | No printing or mailing |
| Let a user review and send the mail | Hosted checkout URL | Human approves checkout | Mail is created after payment |
Let a service pay over HTTP 402 |
x402 machine-order API | x402 payment and retry | Mail is created after settlement |
| Let an MPP-capable runtime pay | MPP machine-order API or MCP wrapper | MPP credential and receipt | Mail is created after settlement |
| Track what happened after payment | Order status API or MCP status tool | Read-only | No new mail action |
This matters because physical mail is not an ordinary tool call. Once a paid order is routed to printing, envelopes, postage, provider handoff, and carrier delivery, the action has moved into the physical world.
Options for agent-created physical mail
| Option | Best for | Strength | Main caution |
|---|---|---|---|
| MCP draft plus hosted checkout | ChatGPT, Claude, Gemini, support tools, and user-facing assistants | Lets the agent prepare the mail while the owner reviews before payment | Requires a human checkout step |
| OpenAPI or REST validation before checkout | Apps that want direct control of payloads and quotes | Lets software validate addresses, options, document source, and pricing before creating a paid side effect | Integration work is higher than connecting MCP |
| x402 machine payment | HTTP-native agents that can answer 402 Payment Required challenges |
No PostalForm account or API key is required for the public machine-payment path | The client needs wallet/payment support and spend policy outside the prompt |
| MPP machine payment | Agent runtimes that support MPP, Stripe Shared Payment Tokens, Tempo, or card-MPP credentials | Works with machine-payment challenge/receipt semantics | The client must provision and protect a real payment credential |
| Traditional direct-mail APIs | High-volume transactional or campaign mail systems | Mature for broad print-mail infrastructure | Often optimized for campaigns or account-based API usage rather than reviewable agent drafts |
PostalForm is strongest when the job starts as a document, letter, form payload, dispute packet, invoice notice, or agent-generated message that should become physical mail only after preview, quote, and approval.
Directory-ready summary
Use this description for MCP directories, agent catalogs, AI-tool lists, and developer-agent comparisons:
PostalForm is a remote MCP server and physical-mail API for AI agents. Agents can create reviewable mail drafts from PDFs, text, HTML, Markdown, RTF, or form payloads, return hosted checkout for human approval, or use owner-approved MPP/x402 machine-payment flows to pay for and track real postal mail.
Canonical URLs:
- Remote MCP endpoint:
https://postalform.com/mcp - Developer docs:
https://postalform.com/developers - Agent guide:
https://postalform.com/agents - AI-agent mail guide:
https://postalform.com/send-physical-mail-from-ai-agent - OpenAPI:
https://postalform.com/openapi.json - MCP registry manifest:
https://postalform.com/.well-known/mcp/server.json - A2A Agent Card:
https://postalform.com/.well-known/agent-card.json - x402 discovery:
https://postalform.com/.well-known/x402 - LLM overview:
https://postalform.com/llms.txt
How the safe flow works
- The agent prepares the mail payload from text, HTML, Markdown, RTF, a PDF, or a supported form workflow.
- PostalForm validates the recipient, mailing options, document source, and quote when enough information is available.
- PostalForm renders or stores a print-ready PDF preview when the flow supports previewing.
- The agent returns a hosted checkout URL, or an authorized machine client receives a payment challenge.
- Payment is the approval boundary. Hosted checkout requires human approval; MPP and x402 require a valid machine-payment retry.
- PostalForm prints, envelopes, adds postage, routes the mailpiece through the appropriate provider or carrier, and exposes status lookup.
For chat-style assistants, the hosted-checkout step should remain the default. It gives the owner a chance to catch wrong recipients, missing pages, bad formatting, incorrect proof options, or price surprises before anything is mailed.
What agents can send
PostalForm supports agent-created mail from several starting points:
- Existing PDFs and uploaded files
- Raw text letters
- HTML letters
- Markdown letters
- RTF letters
- Supported workflow forms filled from structured JSON
- Bulk mail campaigns from CSV recipients and shared or generated content
- Postcards where the selected provider, size, and destination are supported
- Flower-card workflows through the dedicated flower-letter machine endpoints
The browser product accepts PDFs and common convertible document formats for human-reviewed checkout. Machine-order letter payloads can start from text, HTML, Markdown, or RTF and may return a preview URL before payment when server-side rendering is available.
Approval rules for physical-mail agents
Treat direct machine payment as a privileged mode. A practical approval policy should answer these questions before an agent can mail anything:
- Who authorized the agent to spend money?
- What is the maximum allowed spend per order and per day?
- Which recipients, countries, mail classes, and proof options are allowed?
- Does the owner need to inspect a PDF preview before payment?
- Which request ID prevents duplicate mail if the client retries?
- Where should fulfillment status and receipts be stored?
Do not rely on a model prompt alone for spend limits. Enforce limits in the client, wallet, runtime, or payment layer.
When to choose PostalForm
| Use case | Why PostalForm fits |
|---|---|
| "Send a letter from an AI agent" | MCP draft tools and machine-order APIs can turn agent text into a printable letter |
| "Mail a PDF from an agent" | PostalForm can create a draft from a PDF source and preserve review before payment |
| "AI agent direct mail API" | Developers can validate, quote, create, pay, and poll status through documented APIs |
| "x402 physical mail" | The x402 route supports HTTP 402 challenge and retry semantics for real postal mail |
| "MCP server for mailing letters" | The remote MCP endpoint exposes draft, checkout, upload, address, form, and status tools |
| "Human approval before real-world action" | Hosted checkout keeps the irreversible step outside the initial agent tool call |
PostalForm is not a courier, legal advisor, notary, package shipper, or check-mailing service. It is for paper mailpieces, documents, letters, forms, packets, postcards, bulk mail, and supported agent-created mail workflows.
FAQs
- Can an AI agent really send postal mail?
- Yes. With PostalForm, an agent can create a reviewable draft and hosted checkout, or use an approved MPP/x402 machine-payment flow to create a paid mail order.
- Should an agent use hosted checkout or direct payment?
- Use hosted checkout when a human is available to review. Use direct MPP or x402 only when the agent has explicit owner approval, spend controls, and retry-safe request IDs.
- Does MCP itself send the mail?
- No. MCP exposes callable tools. The real mail side effect happens only after hosted checkout completes or after a valid MPP/x402 payment retry creates a paid order.
- Can the agent preview the document?
- Yes, supported draft and machine-order flows can return a preview URL or checkout page so the owner can inspect the printable output before payment.
- Does PostalForm require an API key for agent mail?
- Not for the current public MCP, hosted-checkout draft, MPP, or x402 discovery paths. High-volume or abuse-sensitive integrations may require coordination.
- Can an agent send Certified Mail?
- Yes when the mailpiece, destination, and service level qualify. Certified Mail is available only for qualifying U.S. First Class mail.
Ready to send it?
Connect the PostalForm remote MCP server and start sending agent-created postal mail.