--- title: "Send physical mail from Claude" description: "Connect Claude to Sincerely and send real B2B direct mail. Claude Code takes one command, claude.ai and Claude Desktop take a custom connector, and a human confirms before anything prints." canonical: https://trysincerely.com/integrations/claude-mcp last_updated: 2026-09-06 --- > 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. # Send physical mail from Claude > Connect Claude to Sincerely and send real B2B direct mail. Claude Code takes one command, claude.ai and Claude Desktop take a custom connector, and a human confirms before anything prints. Source: https://trysincerely.com/integrations/claude-mcp Yes, Claude can send physical mail through its MCP-capable chat, desktop, mobile, and coding clients. Sincerely is B2B direct mail software that runs an MCP server at `https://trysincerely.com/api/mcp`. Connect the two and Claude can build an audience of target accounts, verify their business addresses, write a piece for each recipient, and stage a campaign. Nothing prints and no money moves until a person reviews a confirmation card and clicks. ## Prompt to paste into Claude ```text Use Sincerely to prepare a letter campaign for the 40 accounts in my Salesforce list called Q4 tier 1. Check the workspace, audience, mailability, drafts, holdout, and credit need. Show me what needs review and stop before launch. ``` ## Which Claude surfaces support this As of August 2026, all the ones people actually work in. [Anthropic's custom connector documentation](https://support.claude.com/en/articles/11175166-get-started-with-custom-connectors-using-remote-mcp) covers claude.ai on the web, Claude Desktop, and the mobile apps; custom connectors are available on every plan, with Free limited to one. Claude Code adds MCP servers [from the command line](https://code.claude.com/docs/en/mcp). Custom connectors reach the server from Anthropic's cloud rather than your device, which is no obstacle here because Sincerely's endpoint is on the public internet. ## Connect Claude Code One command: ```bash claude mcp add --transport http sincerely https://trysincerely.com/api/mcp ``` Then run `/mcp` inside Claude Code and finish the sign-in in your browser. Authentication is OAuth: you sign in to Sincerely yourself, and Claude gets a token scoped to your workspace and your role, so it can never reach anything you cannot. Add `--scope user` to the command if you want the server available in every project instead of the current one. ## Connect claude.ai or Claude Desktop On a Free, Pro, or Max plan, per [Anthropic's steps](https://support.claude.com/en/articles/11175166-get-started-with-custom-connectors-using-remote-mcp): go to Customize, then Connectors, click the plus button, choose "Add custom connector", and paste `https://trysincerely.com/api/mcp`. Free accounts can add one custom connector. On Team and Enterprise plans an Owner adds the connector under Organization settings first, and each member then connects it themselves. Either way the browser OAuth flow runs and you approve the connection as yourself. ## What Claude can do in Sincerely - Build audiences from a description of your ideal customer, a CSV, or your synced CRM data, with business addresses resolved and checked for mailability before anything can print. - Research accounts and write every piece for one recipient from CRM context and dated, sourced facts. - Prepare campaigns end to end: format, budget, cadence, account-level holdouts, and an experiment contract, staged for your sign-off. - Read honest results. Readouts report lift against holdouts with intervals, and say plainly when a number is not ready. ## What Claude cannot do Spend your money alone. Any tool call that prints a piece, launches a campaign, changes suppression, or has another material consequence stops and renders a confirmation card with the exact affected records and consequences. Send and launch previews include the recipients, design proof, and current cost. Only a signed-in person can approve it, and no prompt or connector setting turns the gate off. [How physical mail MCP works](https://trysincerely.com/guides/physical-mail-mcp) explains why the gate is structural rather than a prompt instruction. ## What a revenue team runs from Claude The pattern that works is conversational triggers on real pipeline events. "Mail the eight accounts that went quiet after a demo this month" becomes an audience, eight individually written pieces, and a staged send you approve in one review. Teams run [event follow-up](https://trysincerely.com/playbooks/event-follow-up) the week after a conference, [closed-lost revival](https://trysincerely.com/playbooks/closed-lost-revival) on deals that died on timing, and one-off executive touches when a champion goes dark. Claude does the research and drafting; your click is the send. ## Start free Setup details, the one-off send flow, and campaign launch mechanics are in the [agent quickstart](https://trysincerely.com/docs/agent-quickstart) and the [MCP agents guide](https://trysincerely.com/integrations/mcp-agents). A new workspace starts on a free audit plan, so Claude can connect, build audiences, and draft pieces before you pick a [plan](https://trysincerely.com/pricing). ## Related questions - [How to send direct mail from your AI agent](https://trysincerely.com/integrations/mcp-agents): Connect Claude, Cursor, or another MCP agent to build an audience, draft a piece, and request a send, with human confirmation before money is spent. - [Agent quickstart](https://trysincerely.com/docs/agent-quickstart): Connect an MCP client to a Sincerely workspace in three steps, then learn where the confirmation gate sits and which tools a new workspace can reach. - [Physical mail MCP, how AI agents send real mail](https://trysincerely.com/guides/physical-mail-mcp): What a physical mail MCP server is, what to check before connecting an agent to one, and when wrapping a print API yourself is the better choice. - [The event follow-up play](https://trysincerely.com/playbooks/event-follow-up): Mail a personal note within days of a booth conversation, reference what you actually discussed, and use the piece to set up the meeting ask. --- Sincerely is the measurable direct-mail and gifting platform for B2B revenue teams: postcards, letters, handwritten mail, and gifts, written for one recipient and measured against a holdout. Contact Sincerely: https://trysincerely.com/contact Agent routing index: https://trysincerely.com/llms.txt