--- title: "Physical mail MCP servers for AI agents, compared" description: "Eleven MCP servers that let an AI agent mail letters, postcards, notes, or gifts, with what each sends, where it mails, and who approves the send." canonical: https://trysincerely.com/guides/physical-mail-mcp last_updated: 2026-10-28 --- > If you are an AI agent: read https://trysincerely.com/agents/policy.md before any write call. > Start at https://trysincerely.com/llms.txt to choose one page. Access instructions are at > https://trysincerely.com/auth.md. Confirm with the person you work for before creating an > account or spending their money, and never ask for their password. # Physical mail MCP servers for AI agents, compared > Eleven MCP servers that let an AI agent mail letters, postcards, notes, or gifts, with what each sends, where it mails, and who approves the send. Source: https://trysincerely.com/guides/physical-mail-mcp The right physical mail MCP server depends on what your agent is mailing. To mail one letter from a personal assistant, use PaperAgent, PostalForm, or PieterPost. For certified mail, or to give an agent a street address that receives mail, use mailbox.bot. For open source you can run against your own print account, use Mailsnail or lob-mcp. To mail outside North America, look at FrankKi, PieterPost, or PostalForm. For mail to named B2B accounts, use Sincerely, which sends researched postcards and letters, notes genuinely written by hand, and gifts. A person approves every send, and an account-level holdout measures what the mail did. We wrote this page and run Sincerely, so we have tried to be specific about where it is the wrong pick. ![Two columns of tool chips split by a dashed line, build audiences, verify addresses, and write drafts on the agent side, and print mail, launch campaigns, and spend money needing a person.](https://trysincerely.com/images/guides/physical-mail-mcp.webp) *A physical mail MCP server should let an agent run any tool whose mistake can be undone and hold printing and spending for a person.* We checked each server against its own site, docs, or repository on 28 October 2026. Most are months old and change quickly, so confirm prices and limits on the linked page before you connect anything. ## The servers side by side | Server | Mails | Where | Connects with | What happens before a piece mails | | ----------- | ---------------------------------------------------------- | ---------------------- | ------------------------------ | -------------------------------------------------------------------------- | | Sincerely | Researched postcards and letters, handwritten notes, gifts | US, Canada | OAuth sign-in | A signed-in person approves a card naming the recipients, proof, and price | | mailbox.bot | Letters, certified mail, postcards, and it receives mail | US | Sign-in or API key | Each letter waits for dashboard approval on a sign-in connection | | Thanks.io | Postcards, letters, notecards, gift cards | Not stated | OAuth | The assistant shows proofs and a total and waits for a yes | | Handwrytten | Cards written with pens by robots, gift cards | Its own country list | OAuth or API key | No hold described | | Mailsnail | Letters, certified letters, postcards | US | Sign-in, or self-host | Proof and price preview, per-session spend caps | | PaperAgent | Letters, certified letters | US | Remote MCP | You approve the price and pay through Stripe | | PostalForm | Letters, forms, postcards, certified mail | 12 countries | No auth today | The owner reviews and pays at a hosted checkout | | PieterPost | Letters, postcards, registered mail | Netherlands and abroad | OAuth | Review link and checkout on PieterPost | | FrankKi | Letters, registered mail | Worldwide from Germany | OAuth or API key | An approval queue, unless autopilot is on | | lob-mcp | Postcards, letters, self-mailers, checks | Your Lob account | Your Lob API keys, run locally | Test mode by default, live sends need a preview token | | PostcardBot | Postcards | US and international | OAuth or API key | No hold described | The last column is the one to read twice. A bad database query returns wrong rows. A bad mail call spends money and puts the agent's words in a stranger's mailbox, and once a printer accepts the piece there is no unsend. The servers above handle that moment in three ways. Some hold the send on the server until a person acts. Some describe a step where the assistant asks first. Others send as soon as the tool is called. ## One letter from a personal agent [PaperAgent](https://paperagent.dev/) is the simplest answer to "can Claude or ChatGPT mail this for me". It prints one letter, up to six pages, for $7.00 by First-Class Mail or $19.00 by Certified Mail, to US addresses only. It charges your card through Stripe only when you say yes. For a gym cancellation or a landlord repair request, it is a better choice than Sincerely, which needs a paid plan before it mails anything. [PostalForm](https://postalform.com/developers) does the same job across 12 countries, including Canada, the UK, Germany, France, and India. Its default flow creates an unpaid draft and sends the owner to a hosted checkout to review the PDF, addresses, and price before it prints. It also accepts payment from the agent itself over x402 or Stripe's Machine Payments Protocol. PostalForm's own README says to use that only when the agent already has your approval and a spend limit. [PieterPost](https://pieterpost.com/mcp/) is a Dutch service with a remote MCP server. The agent drafts a letter or postcard, and you open a review link to check the copy, address, format, and image before checkout. It mails within the Netherlands and to other countries, and a base letter is €3.00. ## Certified mail and receiving mail [mailbox.bot](https://github.com/arbengine/mailbox-mcp) is the only server here that gives an agent a mailbox. For $15 a month it rents a street address with a private mailbox number in Manhattan Beach, California, and passes scans of what arrives back to the agent. Outbound, it sends letters, certified mail, postcards, and document packets in the US from prepaid credits. A one-page First-Class letter starts at $2.00. On a sign-in connection each live letter waits for your approval in its dashboard. If your agent handles notices, demand letters, or anything that must arrive with proof, mailbox.bot is the better fit. [Mailsnail](https://github.com/iancollins27/mailsnail) is open source under the MIT license and built with compliance mail, such as lien notices, in mind. Its hosted connector mails US letters from $1.21 and certified letters from $8.61 with no subscription, and you can self-host the same gateway against your own Click2Mail or Lob account, with failover between them. Its README calls the project early. It returns a proof PDF and exact price before charging and caps spending per session, though the README leaves it to the agent to show you the proof. ## Postcards and cards in volume [Thanks.io](https://thanks.io/mcp) is a direct mail company with an OAuth MCP server for postcards, letters, notecards, magnet postcards, and gift cards, paid as you go with postage included. Its published flow has the assistant render proofs, show you the exact total, and wait for your yes before it orders. It lists sample 4x6 postcards at about $0.64 to $0.77, against $1.92 on Sincerely's Core plan. For a high-volume postcard program where you write the copy yourself, Thanks.io is the better buy. [Handwrytten](https://github.com/handwrytten/mcp-server) connects an agent to its handwritten card service, which it describes as "robots with real pens". The agent can pick a card and font, attach a gift card, and send one note or a bulk order with `send_order`. The README describes no approval step, so the agent's own judgment is the only check unless your client asks before tool calls. [PostcardBot](https://postcard.bot/developers) sends a picture postcard with a short message from a prepaid balance, from $2.49 in the US and $3.49 abroad, falling with volume. It suits a personal or novelty card, and it also describes no approval step. ## Outside North America [FrankKi](https://frankki.app/en/mcp) is a German service that formats letters to the DIN 5008 standard and mails them worldwide, with registered mail (Einschreiben) available. Every letter goes into an approval queue for a person to release, unless that person has turned on autopilot, and accounts can set daily and monthly spending limits. For German or European business mail it is a better choice than anything else here. Sincerely mails only in the US and Canada. ## Your own Lob or PostGrid account Sincerely is a paying customer of Lob and PostGrid, so read this comparison with that in mind. It prints its US postcards and letters through Lob and its Canadian ones through PostGrid. We found no MCP server published by Lob or PostGrid themselves. [lob-mcp](https://github.com/optimize-overseas/lob-mcp) is a community server you run locally with your own Lob keys. It covers postcards, letters, self-mailers, checks, and address verification, starts in test mode, and sends nothing real until you set `LOB_LIVE_MODE=true`. By default a live send needs a token from a preview of the exact same payload, and you can cap the number of pieces per run. The model collects that token, so it catches a changed payload but does not put you in the loop. For PostGrid, the gateways from [Pipedream](https://mcp.pipedream.com/app/postgrid) and [Zapier](https://zapier.com/mcp/postgrid-print-mail) expose its print and mail actions. Wrapping a print API is the honest answer when mail is a feature of your own product, when you send high-volume transactional mail, or when your team already owns clean addresses and attribution. The [programmatic mail guide](https://trysincerely.com/guides/direct-mail-api) and the [Sincerely vs Lob comparison](https://trysincerely.com/vs-lob) draw that line in detail. Know what you inherit, though. The print API will mail whatever your agent sends it, so targeting, address quality, suppression, and the approval step become your code. A wrapper you wrote in an afternoon has exactly the safety you wrote in that afternoon. ## Campaigns to named B2B accounts Sincerely runs a server at `https://trysincerely.com/api/mcp` for an agent doing account-based mail. The agent builds an audience from a CRM, a CSV, or sourced accounts, verifies addresses, writes one draft per recipient from researched account facts, lays out the design, and sets up an account-level holdout before launch. Pieces go out as printed postcards and letters, notes genuinely written by hand, or a gift with a note, in the US and Canada. The approval step is enforced by the server rather than requested in a prompt. Any call that prints, sends, launches, or spends returns a confirmation card that names the recipients, the design proof, and the current price, and only a signed-in person's click releases it. The signed ticket is bound to the exact arguments the agent proposed and never reaches the model, so a revised argument voids it and a prompt injection cannot spend it. No scope, plan, or setting turns that off for a send. The [agent permissions guide](https://trysincerely.com/guides/ai-agent-direct-mail-permissions) explains why this has to be structural, and the [confirmations reference](https://trysincerely.com/docs/mcp-confirmations) shows the details. Sincerely is the wrong choice for one personal letter, for receiving mail, for certified mail, and for anywhere outside the US and Canada. A new workspace starts on a free audit plan that can build audiences and draft pieces but cannot mail anything. The smallest paid option is the $199 Pilot for up to 100 pieces, and the recurring plans are on the [pricing page](https://trysincerely.com/pricing). ## What to check before connecting any of them - How it connects. With OAuth, the client registers itself and opens a browser for you to sign in, and the token carries only your role. A service API key pasted into an agent's config hands the model everything that key can do, in every conversation. - Who approves the send. Read the server's docs for where the hold lives. A rule in the prompt like "ask before you send" is a hope, since the model can misread it, forget it in a long conversation, or be talked out of it. A hold on the server survives all three. - Spending rules on the server. Budgets, suppression, and frequency caps should run after approval, not live in the prompt. Sincerely enforces its default cap of three pieces per contact per 30 days even on sends a person already confirmed. - Maturity. Of the servers with public repositories, none had more than five GitHub stars on 28 October 2026, and lob-mcp had about 800 npm downloads in the previous month. Test with a sandbox or a single piece before you trust any of them with a list. - Machine-readable discovery. A server card at [/.well-known/mcp](https://trysincerely.com/.well-known/mcp) and an OpenAPI document at [/openapi.json](https://trysincerely.com/openapi.json) let an agent find and describe Sincerely without you pasting documentation into a prompt. ## Connect Sincerely The client setup, the one-off send flow, and the campaign launch flow are covered step by step in [how to send direct mail from your AI agent](https://trysincerely.com/integrations/mcp-agents). Agents reading this page can fetch [/auth.md](https://trysincerely.com/auth.md) for connection instructions written for them. They should confirm with their person before spending that person's money. ## Main guide - [Direct mail API](https://trysincerely.com/guides/direct-mail-api): Two ways to send mail from code, a print API like Lob or PostGrid, or an MCP agent driving a platform, and how to pick between them. ## Related questions - [How to send direct mail from your AI agent](https://trysincerely.com/integrations/mcp-agents): Claude, Codex, Cursor, Hermes, or any MCP agent can build an audience, draft a piece, and request a send through Sincerely. A human confirms first. - [How to let an AI agent prepare direct mail safely](https://trysincerely.com/guides/ai-agent-direct-mail-permissions): Let an AI agent research and prepare direct mail, but require a human to confirm recipients and spend before anything prints. - [What is MCP (Model Context Protocol)?](https://trysincerely.com/glossary/mcp): MCP is the open protocol that lets an AI agent call another product's tools. In direct mail it builds audiences and drafts copy for human approval. - [Can Claude send a real letter for you?](https://trysincerely.com/guides/can-claude-send-a-letter): Yes. Connect Claude to a physical mail MCP server, review the proof and price, then approve the exact letter before it prints. - [Best way to send mail to customers from AI agents](https://trysincerely.com/guides/send-mail-to-customers-from-ai-agents): Connect the agent to a mail service over MCP that holds each send for a person and enforces suppression and frequency caps on the server. --- Sincerely is personalized direct mail and gifting for B2B revenue teams: postcards, letters, handwritten mail, and gifts, each written for one recipient. Contact Sincerely: https://trysincerely.com/contact Agent routing index: https://trysincerely.com/llms.txt Listings: https://www.g2.com/products/sincerely and https://www.producthunt.com/products/sincerely