How do I install Mailsnail?

Mailsnail is a local plugin. Install it using npm package: mailsnail and add the generated configuration snippet to your AI app's MCP config file. Then restart your AI app.

Is Mailsnail safe to use?

Yes. Mailsnail passed MCP Marketplace's automated security scan with a score of 9.7/10 (low risk). Every server on MCP Marketplace is security-scanned before it's listed; see the full security report on this page for the findings and permissions.

What credentials does Mailsnail need?

Mailsnail requires the following credentials or environment variables: MAIL_PROVIDER, MAIL_API_BASE_URL, CLICK2MAIL_USERNAME, CLICK2MAIL_PASSWORD, LOB_API_KEY, MAIL_MCP_ALLOW_LIVE, MAIL_MCP_SPEND_CAP_USD. You can find setup instructions on the server detail page.

What AI apps work with Mailsnail?

Mailsnail uses the Model Context Protocol (MCP) and works with any MCP-compatible AI app, including Claude, ChatGPT / Codex, Gemini, Copilot, Cursor, and more.

Back to Browse

Mailsnail MCP Server

by Iancollins27

Developer ToolsLow Risk9.7MCP RegistryLocal

Free

Server data from the Official MCP Registry

Send USPS letters, postcards & certified mail from any agent. No signup; pay-per-piece via Stripe.

About

Send USPS letters, postcards & certified mail from any agent. No signup; pay-per-piece via Stripe.

Security Report

9.7

Low Risk9.7Low Risk

Valid MCP server (2 strong, 4 medium validity signals). No known CVEs in dependencies. ⚠️ Package registry links to a different repository than scanned source. Imported from the Official MCP Registry. 1 finding(s) downgraded by scanner intelligence.

10 files analyzed · 1 issue found

Security scores are indicators to help you make informed decisions, not guarantees. Always review permissions before connecting any MCP server.

Permissions Required

This plugin requests these system permissions. Most are normal for its category.

HTTP Network Access

Connects to external APIs or services over the internet.

env_vars

Check that this permission is expected for this type of plugin.

file_system

Check that this permission is expected for this type of plugin.

database

Check that this permission is expected for this type of plugin.

What You'll Need

Set these up before or after installing:

Where to mail from: 'managed' (default, no signup, pay-per-piece via Stripe), 'click2mail' (BYO account), or 'lob' (BYO key).Optional

Environment variable: MAIL_PROVIDER

Hosted Mailsnail backend. Required when MAIL_PROVIDER=managed.Optional

Environment variable: MAIL_API_BASE_URL

Click2Mail account username. Required when MAIL_PROVIDER=click2mail.Optional

Environment variable: CLICK2MAIL_USERNAME

Click2Mail account password. Required when MAIL_PROVIDER=click2mail.Required

Environment variable: CLICK2MAIL_PASSWORD

Lob API key. Required when MAIL_PROVIDER=lob. test_* is free; live_* actually mails.Required

Environment variable: LOB_API_KEY

Set to '1' to actually mail in BYOK modes. Default '0' is dry-run.Optional

Environment variable: MAIL_MCP_ALLOW_LIVE

Per-session estimated spend cap. Server refuses sends past this.Optional

Environment variable: MAIL_MCP_SPEND_CAP_USD

How to Install

Add this to your MCP configuration file:

{
  "mcpServers": {
    "io-github-iancollins27-mailsnail": {
      "env": {
        "LOB_API_KEY": "your-lob-api-key-here",
        "MAIL_PROVIDER": "your-mail-provider-here",
        "MAIL_API_BASE_URL": "your-mail-api-base-url-here",
        "CLICK2MAIL_PASSWORD": "your-click2mail-password-here",
        "CLICK2MAIL_USERNAME": "your-click2mail-username-here",
        "MAIL_MCP_ALLOW_LIVE": "your-mail-mcp-allow-live-here",
        "MAIL_MCP_SPEND_CAP_USD": "your-mail-mcp-spend-cap-usd-here"
      },
      "args": [
        "-y",
        "mailsnail"
      ],
      "command": "npx"
    }
  }
}

Documentation

View on GitHub

From the project's GitHub README.

Mailsnail

Open-source, provider-agnostic physical mail for AI agents.

Agents have every channel except one. They can email, text, call, and post to every feed — but until now, putting a real, postmarked envelope in a mailbox meant a human signing up for a print-provider account, provisioning API keys, and wiring billing. Mailsnail closes that gap:

No signup in managed mode. Agents pay per piece via Stripe Shared Payment Tokens over the Machine Payments Protocol (HTTP 402). First letter can go out minutes after install. $1.50 first-class, $9.00 certified, $1.00 postcard — flat, no subscription.
No lock-in, ever. The provider layer is open and swappable: bring your own Click2Mail or Lob account, self-host the whole gateway, or chain providers for failover. The managed service is a convenience, not a cage.
Built for compliance mail. Certified letters with extra_service: "certified" — the mail that legally must be physical (preliminary lien notices, legal notices) and must not miss its deadline because one print API had a bad day.

claude mcp add mailsnail -- npx -y mailsnail
# then: "Send me a postcard that says hello."

Packages

Package	What it is
`mailsnail`	MCP server — 7 tools (`verify_address`, `preview_letter`, `send_letter`, `send_postcard`, `get_letter`, `list_letters`, `cancel_letter`) over any provider below. Works in Claude Code, Claude Desktop, Cursor, Codex CLI, OpenAI Agents SDK.
`@mailsnail/core`	Provider-agnostic core: adapters (Click2Mail, Lob, any Mailsnail gateway), multi-provider failover router, request validation. Zero dependencies.
`@mailsnail/gateway`	Self-hostable REST API: BYO provider credentials, `body_text`→PDF rendering, proofs, invocation logging. The managed service at `api.mailsnail.dev` runs the same wire protocol.
`spec/`	The provider-neutral mail-piece schema + the failover-safety contract. Implement it and anything — including a print shop — becomes a Mailsnail-compatible node.

Four ways to run it

Mode	Credentials	Paying	Good for
managed (default)	none	agent, per piece (Stripe SPT)	agents; zero-setup
gateway	your own, on your server	your provider account	teams; PII stays in your infra
click2mail / lob (BYOK)	yours, local env	your provider account	direct control, one provider
failover chain	yours, per provider	your provider accounts	mail that must not miss deadlines

Failover is deliberately conservative: a send moves to the next provider only when the failed provider guarantees nothing entered production and no money moved (safeToRetry — see the spec). A duplicate certified letter is worse than an error.

Safety

Dry-run by default everywhere; live mail requires an explicit MAIL_MCP_ALLOW_LIVE=1.
Per-session spend caps in the MCP server; auto-refund in managed mode when a paid piece fails to mail.
preview_letter returns a proof PDF and exact price before anything is charged — show it to your user first.
Don't use this for spam, harassment, or fraud. Provider terms and USPS regulations apply; managed mode enforces its own abuse screening.

Why open source

You're letting software put paper in mailboxes and spend money doing it. Read the code. Run it yourself with your own provider account for free. Use managed mode when you'd rather not hold credentials at all. If we ever disappoint you, MAIL_PROVIDER=click2mail and your mail keeps moving — that's the deal, and it's enforceable because this repo exists.

Status

Early. US-only today. Letters, certified letters, and postcards. The managed API, MCP server, self-host gateway, and Click2Mail/Lob adapters are live; additional adapters (PostGrid, Stannp) are next — CONTRIBUTING.md has the adapter guide if you want one sooner.

License

MIT.

Reviews

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Mailsnail MCP Server

About

Security Report

Findings (1)

Permissions Required

What You'll Need

How to Install

Documentation

Mailsnail

Packages

Four ways to run it

Safety

Why open source

Status

License

Reviews

No reviews yet

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