JMAP MCP Server

A Deno workspace containing a functional JMAP email client and a Model Context Protocol (MCP) server built on top of it. The client package uses jmap-jam for JMAP protocol access; the MCP package adapts those typed operations into tools.

Features

Email Management Tools

• Search Emails: Search emails with text queries, sender/recipient filters, date ranges, and keywords. All filters are AND'd together.

• Get Emails: Retrieve specific emails by ID with configurable property selection

• Get Threads: Retrieve email threads (conversation chains)

• Mark Emails: Mark emails as read/unread, flagged/unflagged

• Move Emails: Move emails to one mailbox

• Patch Email Mailboxes: Add or remove selected mailbox memberships while preserving unspecified memberships

• Delete Emails: Delete emails permanently

Mailbox Management

• Get Mailboxes: List all mailboxes/folders with hierarchy support. Use this to find mailbox IDs needed by other tools.

Incremental Sync

• Get Email Changes: Get IDs of emails created, updated, or destroyed since a previous state (state-based delta tracking)

• Get Search Updates: Get additions/removals within a previous search query since its last queryState

Email Composition

• Send Email: Compose and send new emails with support for plain text and HTML

• Reply to Email: Reply to existing emails with automatic header handling and reply-all support

Key Capabilities

• Full JMAP RFC 8620/8621 compliance via jmap-jam

• Comprehensive input validation with Zod schemas

• Pagination support for all list operations

• State-based incremental sync for efficient polling

• Rich error handling and connection management

• Capability-based tool registration (read-only, submission)

• TypeScript support with strong typing

Reusable JMAP Client

Standalone applications can import @wyattjoh/jmap without creating an MCP server or transport:

import { connectJmap, searchEmails } from "jsr:@wyattjoh/jmap";

const connection = await connectJmap({
  sessionUrl: Deno.env.get("JMAP_SESSION_URL")!,
  bearerToken: Deno.env.get("JMAP_BEARER_TOKEN")!,
  accountId: Deno.env.get("JMAP_ACCOUNT_ID"),
});

const unread = await searchEmails(connection, {
  filter: { inMailbox: "inbox-id", notKeyword: "$seen" },
  limit: 50,
  position: 0,
});

See packages/jmap/README.md for the client package.

Related MCP server: bare-mcp

Installation

Claude Code Plugin (Recommended)

Install via the plugin marketplace:

/plugin marketplace add wyattjoh/claude-code-marketplace
/plugin install jmap-mcp@wyattjoh-marketplace

Then configure the required environment variables in your MCP server settings.

Prerequisites

• Deno v2 or later

• A JMAP-compliant email server (e.g., Cyrus IMAP, Stalwart Mail Server, FastMail)

• Valid JMAP authentication credentials

Setup

Add the following to your agent of choice:

{
  "mcpServers": {
    "jmap": {
      "type": "stdio",
      "command": "deno",
      "args": [
        "run",
        "--allow-net=api.fastmail.com",
        "--allow-env=JMAP_SESSION_URL,JMAP_BEARER_TOKEN,JMAP_ACCOUNT_ID",
        "jsr:@wyattjoh/jmap-mcp@0.6.5"
      ],
      "env": {
        "JMAP_SESSION_URL": "https://api.fastmail.com/jmap/session",
        "JMAP_BEARER_TOKEN": "YOUR_API_TOKEN"
      }
    }
  }
}

Replace api.fastmail.com in --allow-net with your JMAP server's hostname if not using FastMail.

Usage

Environment Variables

Available Tools

get_mailboxes

List mailboxes/folders with their IDs, names, and metadata. Call this first to get mailbox IDs needed by search_emails (inMailbox) and move_emails (mailboxId). Common names: Inbox, Drafts, Sent, Trash, Archive, Spam/Junk.

Parameters:

• parentId (optional): Filter by parent mailbox ID

• limit (optional): Max results (1-200, default: 100)

• position (optional): Starting position for pagination

search_emails

Search emails with filters. All filters are AND'd together. Returns only email IDs — use get_emails to fetch content. Results include queryState for incremental sync via get_search_updates.

Parameters:

• query (optional): Text search across all fields

• body (optional): Search in message body only

• from (optional): Filter by sender email address

• to (optional): Filter by recipient email address

• subject (optional): Filter by subject text

• inMailbox (optional): Mailbox ID to search within (get from get_mailboxes)

• hasKeyword (optional): Filter by keyword (e.g., $seen, $flagged)

• notKeyword (optional): Exclude by keyword (e.g., $seen, $draft)

• allInThreadHaveKeyword (optional): All emails in thread must have keyword

• someInThreadHaveKeyword (optional): At least one email in thread must have keyword

• before (optional): Only emails before date (ISO 8601 datetime)

• after (optional): Only emails after date (ISO 8601 datetime)

• limit (optional): Max results (1-100, default: 50)

• position (optional): Starting position for pagination (default: 0)

get_emails

Retrieve specific emails by their IDs. Use properties to request only what you need — fetching all properties returns large payloads.

Parameters:

• ids: Array of email IDs (1-50 IDs)

• properties (optional): Specific properties to return. Recommended sets:

  • Summary: ["id", "subject", "from", "to", "receivedAt", "preview"]

  • Full read: ["id", "subject", "from", "to", "cc", "receivedAt", "bodyValues", "textBody", "htmlBody"]

  • Note: To get body content, include bodyValues AND textBody/htmlBody

get_threads

Get email threads by their IDs. Thread IDs come from get_emails responses (threadId property). Returns email IDs per thread — use get_emails on those IDs to fetch content.

Parameters:

• ids: Array of thread IDs (1-20 IDs)

get_email_changes

Get IDs of emails created, updated, or destroyed since a previous state. Use the state string from a get_emails response.

Parameters:

• sinceState: State string from a previous get_emails response

• maxChanges (optional): Max changes to return (1-500)

• fetchEmails (optional): Auto-fetch full email details for changed IDs (default: false)

• properties (optional): Properties to fetch when fetchEmails is true

get_search_updates

Get changes within a previous search query since its queryState. Must use the same filter parameters as the original search_emails call.

Parameters:

• sinceQueryState: queryState from a previous search_emails response

• All filter parameters from search_emails (must match original query)

• maxChanges (optional): Max changes to return (1-500)

mark_emails

Mark emails as read/unread or flagged/unflagged.

Parameters:

• ids: Array of email IDs (1-100 IDs)

• seen (optional): Mark as read (true) or unread (false)

• flagged (optional): Mark as flagged (true) or unflagged (false)

move_emails

Move emails to a different mailbox. Use get_mailboxes to find the target mailbox ID.

Parameters:

• ids: Array of email IDs (1-100 IDs)

• mailboxId: Target mailbox ID (get from get_mailboxes)

patch_email_mailboxes

Add or remove selected mailbox memberships without replacing unspecified memberships. This supports label-like workflows and compound categorization.

Parameters:

• ids: Array of email IDs (1-100 IDs)

• addMailboxIds (optional): Mailbox IDs to add

• removeMailboxIds (optional): Mailbox IDs to remove

At least one mailbox must be added or removed. A mailbox cannot appear in both arrays.

delete_emails

Delete emails permanently (cannot be undone). Prefer moving to Trash via move_emails for recoverable deletion.

Parameters:

• ids: Array of email IDs (1-100 IDs)

send_email

Send a new email. Requires either textBody or htmlBody (or both).

Parameters:

• to: Array of recipients (name optional, email required)

• cc (optional): Array of CC recipients

• bcc (optional): Array of BCC recipients

• subject: Email subject

• textBody (optional): Plain text body

• htmlBody (optional): HTML body

• identityId (optional): JMAP identity ID to send from (uses server default if omitted)

reply_to_email

Reply to an existing email. Automatically sets To/CC, Re: subject prefix, and threading headers (In-Reply-To, References).

Parameters:

• emailId: ID of email to reply to

• replyAll (optional): Include all original recipients (default: false)

• subject (optional): Custom reply subject (defaults to Re: <original>)

• textBody (optional): Plain text body

• htmlBody (optional): HTML body

• identityId (optional): JMAP identity ID to send from (uses server default if omitted)

JMAP Server Compatibility

This server should work with any JMAP-compliant email server, including:

• Cyrus IMAP 3.0+

• Stalwart Mail Server

• FastMail (commercial)

• Apache James (with JMAP support)

Development

Running in Development

deno task watch     # Run with file watching
deno task start     # Run without watching

Testing

deno task test      # Run all tests
deno task check     # Type-check both packages
deno task lint      # Lint workspace packages
deno task fmt       # Format code
deno task publish:check # Validate both JSR packages

Architecture

The repository is a Deno workspace with two independently publishable packages:

• packages/jmap / @wyattjoh/jmap: Functional connection, retrieval, incremental sync, mutation, and submission operations

• packages/jmap-mcp / @wyattjoh/jmap-mcp: MCP schemas, tool adapters, capability registration, and stdio entrypoint

The MCP adapters call the client package directly. JMAP behavior belongs in the client package; transport validation and user-facing tool contracts belong in the MCP package.

Security

• All input is validated using Zod schemas

• Environment variables are used for sensitive configuration

• No secrets are logged or exposed in responses

• Follows JMAP security best practices

Contributing

1. Fork the repository

2. Create a feature branch

3. Make changes following the functional programming style

4. Test your changes thoroughly

5. Submit a pull request

License

MIT License - see LICENSE file for details.

Related Projects

• jmap-jam - JMAP client library

• Model Context Protocol - MCP specification

• JMAP RFC 8620 - JMAP core protocol

• JMAP RFC 8621 - JMAP for Mail