Lettio MCP is a Model Context Protocol (MCP) server used to connect AI agents to Lettio mailboxes and perform email operations through the JMAP open standard. Its core goal is to enable AI assistants to read, search, reply to, and send emails while ensuring that email data does not leave Europe.
In terms of purpose, this tool mainly serves users who want to let AI assistants handle mailbox matters. AI assistants can organize the inbox, find specific emails, and send replies, all based on EU-hosted mailboxes without going through third-party intermediaries.
Main capabilities include: listing emails, searching emails, reading emails, and sending emails, all implemented through the JMAP standard. It supports configuring a single mailbox account or multiple mailbox accounts. When multiple accounts are configured, the account parameter can be used when calling tools to specify which mailbox to use. The sending function is deliberately restricted: before sending, the server queries the mail host for the identities allowed for the logged-in mailbox and requires one of the identities to match the login address; both the From header and the SMTP envelope MAIL FROM are fixed to that address, and there is no parameter to choose another sender, so the agent cannot send emails from an external or arbitrary mailbox. Credentials are read from environment variables, kept only in memory, and are not logged.
In terms of usage, users can choose local self-hosting or use a hosted service. The local method requires Node.js 18 or later, as well as a Lettio mailbox and the corresponding app password (it is recommended to use a dedicated app password rather than the main login password). Configuration is done entirely through environment variables. For Claude Desktop, the configuration can be added to claude_desktop_config.json, and after restarting, the Lettio tools will appear in the tools menu. If configuring multiple mailboxes, LETTIO_ACCOUNTS can be set to a JSON array and the single-account variables omitted, after which account: "work" can be passed in any tool to select the mailbox. If you do not want to install anything, you can also use the hosted OAuth-secure MCP server at https://mcp.lettio.eu/mcp，在客户端中添加该 URL and log in.
Applicable scenarios include: privacy-sensitive scenarios that require an AI assistant to automatically classify and organize the inbox, find historical emails, and draft and send replies, while requiring data to be stored within the EU and avoiding third-party involvement. It is also suitable for users who need to manage multiple mailbox accounts.
In terms of limitations, this tool depends on Lettio mailboxes and the JMAP protocol, and the sending identity is strictly fixed, so it cannot send from other addresses. Running locally requires Node.js 18 or later. Information such as fees, pricing, and the specific scope of platform support is not provided in the materials.
