Lettio MCP — Claude Code MCP server: agent email over JMAP
Wires an AI agent to a Lettio mailbox over the open JMAP protocol, so it can read, search, reply and send mail.
claude mcp add --transport http mcp https://mcp.lettio.eu/mcpWhat Lettio MCP does
Lettio MCP is a Model Context Protocol server that gives an agent access to a Lettio mailbox through JMAP. It ships ten tools: account and folder listings, recent messages, free-text search over sender, subject and body, reading one message by id, sending, in-thread reply with an optional reply-all, read/unread toggling, flagging, and moving a message to archive, trash or a named folder.
Sending is locked down on purpose. The server first asks the mail host which addresses the logged-in mailbox may use, then requires a match with the login address. Both the From header and the SMTP envelope MAIL FROM are pinned to it, and no tool parameter lets an agent pick a different sender. Credentials come from environment variables, stay in memory and are never logged.
You need Node.js 18 or newer plus a dedicated app password for the mailbox — not your main login. One mailbox is configured with LETTIO_USERNAME and LETTIO_PASSWORD; for several, set LETTIO_ACCOUNTS to a JSON array and pass account to each tool. A hosted OAuth option lives at https://mcp.lettio.eu/mcp if you would rather not run anything locally.
What it helps with
- triage an inbox and file messages into folders
- find a message by sender or subject
- reply in-thread without breaking the conversation
- send mail as the connected mailbox
- mark a message read or star it
Example prompts for the agent
- List my latest inbox messages and mark them read
- Find emails from the client this week and move them to
archive - Reply to message id 42 and keep the thread
How to install Lettio MCP
1Platform CLI: remote server
claude mcp add --transport http mcp https://mcp.lettio.eu/mcp2Platform CLI
claude mcp add --env LETTIO_USERNAME=<LETTIO_USERNAME> --env LETTIO_PASSWORD=<LETTIO_PASSWORD> --env LETTIO_HOST=<LETTIO_HOST> --transport stdio lettio-mcp -- npx -y @lettio/mcpReplace <…> with your own values
1Platform CLI: remote server
codex mcp add lettio-mcp --url https://mcp.lettio.eu/mcp2Platform CLI
codex mcp add lettio-mcp --env LETTIO_USERNAME=<LETTIO_USERNAME> --env LETTIO_PASSWORD=<LETTIO_PASSWORD> --env LETTIO_HOST=<LETTIO_HOST> -- npx -y @lettio/mcpReplace <…> with your own values
Config file
{
"mcpServers": {
"lettio-mcp": {
"url": "https://mcp.lettio.eu/mcp"
}
}
}{
"mcpServers": {
"lettio-mcp": {
"command": "npx",
"args": [
"-y",
"@lettio/mcp"
],
"env": {
"LETTIO_USERNAME": "<LETTIO_USERNAME>",
"LETTIO_PASSWORD": "<LETTIO_PASSWORD>",
"LETTIO_HOST": "<LETTIO_HOST>"
}
}
}
}Replace <…> with your own values
Config file
{
"servers": {
"lettio-mcp": {
"type": "http",
"url": "https://mcp.lettio.eu/mcp"
}
}
}{
"servers": {
"lettio-mcp": {
"type": "stdio",
"command": "npx",
"args": [
"-y",
"@lettio/mcp"
],
"env": {
"LETTIO_USERNAME": "<LETTIO_USERNAME>",
"LETTIO_PASSWORD": "<LETTIO_PASSWORD>",
"LETTIO_HOST": "<LETTIO_HOST>"
}
}
}
}Replace <…> with your own values
1Platform CLI: remote server
gemini mcp add -t http lettio-mcp https://mcp.lettio.eu/mcp2Platform CLI
gemini mcp add -e LETTIO_USERNAME=<LETTIO_USERNAME> -e LETTIO_PASSWORD=<LETTIO_PASSWORD> -e LETTIO_HOST=<LETTIO_HOST> lettio-mcp npx -y @lettio/mcpReplace <…> with your own values
Step by step, with commands for each platform: How to add an MCP server to Claude Code, Codex, Cursor, VS Code, Gemini CLI and more
Questions about Lettio MCP
How do I install Lettio MCP in Claude Code?
For the local server run `claude mcp add --env LETTIO_USERNAME=<LETTIO_USERNAME> --env LETTIO_PASSWORD=<LETTIO_PASSWORD> --env LETTIO_HOST=<LETTIO_HOST> --transport stdio lettio-mcp -- npx -y @lettio/mcp. For the hosted OAuth server, claude mcp add --transport http mcp https://mcp.lettio.eu/mcp` is enough.
What does Lettio MCP do?
It connects an agent to a Lettio mailbox over JMAP: folder listings, recent messages, search, reading, sending and in-thread replies, plus flags and folder moves.
What do I need to run Lettio MCP?
Node.js 18 or newer and an app password for your Lettio mailbox. To work with several mailboxes, set LETTIO_ACCOUNTS to a JSON array and pass account to the tools.
