Is PostalForm a direct mail API?

Yes. PostalForm is a direct mail API for creating physical-mail drafts and machine-payment mail orders. It is best for document, letter, form, hosted-checkout, and agent-created mail workflows.

Can I mail letters with an API?

Yes. PostalForm can create letter drafts from text, HTML, Markdown, RTF, or PDFs, then return a checkout URL or use approved machine-payment flows.

Do I need an API key?

Not for the current public MCP endpoint or hosted-checkout draft flow. High-volume, abuse-sensitive, or allowlisted production integrations may require coordination with PostalForm.

Can I set print options in the API?

Yes. PostalForm supports options such as color, duplex, delivery speed, Certified Mail where eligible, and mailpiece type depending on the route.

Does the API send mail immediately?

Hosted-checkout drafts do not send mail until the sender pays. Direct machine-payment orders should be used only by approved runtimes with spend controls and idempotent request IDs.

Is PostalForm a marketing automation platform?

No. PostalForm can support bulk and developer workflows, but it is not a CRM campaign suite. Use PostalForm when the core job is turning documents or agent output into reviewable physical mail.

Does PostalForm provide legal advice?

No. PostalForm helps create and send mail, but it does not decide whether a document is legally sufficient or which mailing method a recipient requires.

PostalForm

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Developers

Developer Mail API

PostalForm is a developer mail API for turning PDFs, letters, form packets, and AI-generated content into reviewable physical mail. Use it when your product needs to create a mailing draft, show a printable PDF preview, collect sender and recipient addresses, launch hosted checkout, or let an approved agent pay through MPP or x402.

Published Jan 20, 2026 • Updated May 31, 2026

Explore the API

Direct answer: can developers send postal mail through an API?

Yes. Developers can use PostalForm to create physical-mail drafts and machine-payment mail orders from software. The safest default is hosted checkout: your app or agent prepares the PDF, letter, or form packet, PostalForm returns a preview and checkout URL, and a human reviews the document, addresses, price, and mailing options before payment.

API use cases, answered

Developer query	PostalForm answer	Best destination
`mail letters with an API`	Create a letter draft from text, HTML, Markdown, RTF, or PDF and route the sender to checkout.	`/mail-letters-with-api`
`PDF mail API`	Upload a PDF, create a draft with sender and recipient addresses, and show a preview before payment.	`/mail-pdf-online`
`direct mail API for forms`	Use supported form workflows or upload completed form PDFs, then mail the generated packet.	`/forms`
`Certified Mail API`	Request Certified Mail when the mailpiece and destination qualify; checkout remains the source of truth.	`/certified-mail-online`
`AI agent mail API`	Connect through PostalForm's remote MCP server, hosted checkout, MPP, or x402 flows.	`/agents`
`x402 physical mail API`	Validate an agent-created mail payload, receive an HTTP 402 challenge, pay, retry, and track fulfillment.	`/x402-physical-mail-api`
`machine-payable mail`	Use machine-order REST, MPP, or x402 only with explicit owner approval and spend limits.	`/developers`

Typical hosted-checkout flow

Create a PDF upload - Send the file to PostalForm.
Draft the order - Provide sender/recipient addresses and options.
Launch checkout - Use the checkout URL for payment.
Track status - Read order status after payment.

Hosted checkout is the right default for customer-facing apps, support tools, case-management systems, form workflows, and AI assistants because the mailpiece does not become real mail until the sender reviews and pays.

API vs MCP vs machine payment

Surface	Use it for	Safety default
Developer docs and OpenAPI	Server-side integrations, validation, quotes, draft creation, and status lookups	Validate before creating paid side effects
Remote MCP server	ChatGPT, Claude, Gemini, Cursor, Codex, and other clients that can call MCP tools	Require approval for mail actions
Hosted checkout	Any flow where a person should review the final PDF and price	Use the returned checkout URL
MPP or x402 machine payment	Approved autonomous runtimes that can pay directly	Enforce request IDs, spend limits, and owner approval

Where PostalForm fits among direct-mail APIs

Most direct-mail API comparisons focus on broad campaign platforms: Lob and PostGrid for developer-led transactional mail, Postalytics for CRM-triggered direct mail, Click2Mail for long-running print-to-mail software, and marketing-focused platforms for multi-touch campaigns.

PostalForm is narrower and more reviewable. It is strongest when the workflow begins with a document, letter, form, or agent-generated message that should become physical mail only after preview, address review, and payment approval. It is not trying to replace a full direct-mail marketing suite, CRM campaign platform, or enterprise print network.

If you need	Compare first
Reviewable document mail from a product or assistant	PostalForm
Enterprise-scale transactional print-mail infrastructure	Lob or PostGrid
CRM-triggered multi-touch marketing mail	Postalytics or a marketing automation platform
Broad self-service print-to-mail products	Click2Mail
Real-estate investor drip campaigns	Real-estate-focused platforms such as REmail

What you can automate

Create mailings from internal tools
Send notices, invoices, statements, packets, and form workflows programmatically
Generate letter PDFs from raw text, HTML, Markdown, or RTF
Route customers to hosted checkout for review and payment
Trigger eligible Certified Mail or proof options when available
Build agent-friendly mail flows with MCP, MPP, and x402

Guardrails for real-world mail side effects

Every mail API creates an offline consequence: paper is printed, postage is purchased, and a carrier receives the mailpiece. PostalForm integrations should keep the side effect explicit.

Validate addresses and mail options before creating an order.
Show the sender the final PDF preview when a human is available.
Use hosted checkout for consumer, support, legal-notice, and dispute-letter workflows.
Use MPP or x402 only when the owner has approved autonomous spending.
Store idempotent request IDs so retries do not create duplicate mailings.
Do not use PostalForm to send spam, harassment, illegal content, or documents the sender is not authorized to mail.

Sources

FAQs

Is PostalForm a direct mail API?: Yes. PostalForm is a direct mail API for creating physical-mail drafts and machine-payment mail orders. It is best for document, letter, form, hosted-checkout, and agent-created mail workflows.
Can I mail letters with an API?: Yes. PostalForm can create letter drafts from text, HTML, Markdown, RTF, or PDFs, then return a checkout URL or use approved machine-payment flows.
Do I need an API key?: Not for the current public MCP endpoint or hosted-checkout draft flow. High-volume, abuse-sensitive, or allowlisted production integrations may require coordination with PostalForm.
Can I set print options in the API?: Yes. PostalForm supports options such as color, duplex, delivery speed, Certified Mail where eligible, and mailpiece type depending on the route.
Does the API send mail immediately?: Hosted-checkout drafts do not send mail until the sender pays. Direct machine-payment orders should be used only by approved runtimes with spend controls and idempotent request IDs.
Is PostalForm a marketing automation platform?: No. PostalForm can support bulk and developer workflows, but it is not a CRM campaign suite. Use PostalForm when the core job is turning documents or agent output into reviewable physical mail.
Does PostalForm provide legal advice?: No. PostalForm helps create and send mail, but it does not decide whether a document is legally sufficient or which mailing method a recipient requires.

Ready to send it?

Start with the developer docs and sample requests.