A Model Context Protocol (MCP) server that provides access to the Fastmail API, enabling AI assistants to interact with email, contacts, and calendar data.

• List mailboxes and get mailbox statistics
• List, search, and filter emails with advanced criteria
• Get specific emails by ID with full content
• Send emails (text and HTML) with proper draft/sent handling
• Email management: mark read/unread, delete, move between folders

• Attachment Handling: List and download email attachments
• Threading Support: Get complete conversation threads
• Advanced Search: Multi-criteria filtering (sender, date range, attachments, read status)
• Bulk Operations: Process multiple emails simultaneously
• Statistics & Analytics: Account summaries and mailbox statistics

• List all contacts with full contact information
• Get specific contacts by ID
• Search contacts by name or email

• List all calendars and calendar events
• Get specific calendar events by ID
• Create new calendar events with participants and details

• List available sending identities
• Account summary with comprehensive statistics

• Node.js 18+
• A Fastmail account with API access
• Fastmail API token

1. Clone or download this repository

2. Install dependencies:

   npm install

3. Build the project:

   npm run build

1. Get your Fastmail API token:

   • Log in to Fastmail web interface
   • Go to Settings → Privacy & Security
   • Find "Connected apps & API tokens" section
   • Click "Manage API tokens"
   • Click "New API token"
   • Copy the generated token

2. Set environment variables:

   export FASTMAIL_API_TOKEN="your_api_token_here"
   # Optional: customize base URL (defaults to https://api.fastmail.com)
   export FASTMAIL_BASE_URL="https://api.fastmail.com"

Start the MCP server:

npm start

For development with auto-reload:

npm run dev

Default to main branch:

FASTMAIL_API_TOKEN="your_token" FASTMAIL_BASE_URL="https://api.fastmail.com" \
  npx --yes github:MadLlama25/fastmail-mcp fastmail-mcp

Windows PowerShell:

$env:FASTMAIL_API_TOKEN="your_token"
$env:FASTMAIL_BASE_URL="https://api.fastmail.com"
npx --yes github:MadLlama25/fastmail-mcp fastmail-mcp

Pin to a tagged release:

FASTMAIL_API_TOKEN="your_token" \
  npx --yes github:MadLlama25/fastmail-mcp@v1.6.1 fastmail-mcp

You can install this server as a Desktop Extension for Claude Desktop using the packaged .dxt file.

1. Build and pack:

   npm run build
   npx dxt pack

   This produces fastmail-mcp.dxt in the project root.

2. Install into Claude Desktop:

   • Open the .dxt file, or drag it into Claude Desktop
   • When prompted:
     • Fastmail API Token: paste your token (stored encrypted by Claude)
     • Fastmail Base URL: leave blank to use https://api.fastmail.com (default)

3. Use any of the tools (e.g. get_recent_emails).

🎯 Most Popular Tools:

• check_function_availability: Check what's available and get setup guidance
• test_bulk_operations: Safely test bulk operations with dry-run mode
• send_email: Full-featured email sending with proper draft/sent handling
• advanced_search: Powerful multi-criteria email filtering
• get_recent_emails: Quick access to recent emails from any mailbox

• list_mailboxes: Get all mailboxes in your account
• list_emails: List emails from a specific mailbox or all mailboxes
  • Parameters: mailboxId (optional), limit (default: 20)
• get_email: Get a specific email by ID
  • Parameters: emailId (required)
• send_email: Send an email
  • Parameters: to (required array), cc (optional array), bcc (optional array), from (optional), mailboxId (optional), subject (required), textBody (optional), htmlBody (optional)
• search_emails: Search emails by content
  • Parameters: query (required), limit (default: 20)
• get_recent_emails: Get the most recent emails from a mailbox (inspired by JMAP-Samples top-ten)
  • Parameters: limit (default: 10, max: 50), mailboxName (default: 'inbox')
• mark_email_read: Mark an email as read or unread
  • Parameters: emailId (required), read (default: true)
• delete_email: Delete an email (move to trash)
  • Parameters: emailId (required)
• move_email: Move an email to a different mailbox
  • Parameters: emailId (required), targetMailboxId (required)

• get_email_attachments: Get list of attachments for an email
  • Parameters: emailId (required)
• download_attachment: Get download URL for an email attachment
  • Parameters: emailId (required), attachmentId (required)
• advanced_search: Advanced email search with multiple criteria
  • Parameters: query (optional), from (optional), to (optional), subject (optional), hasAttachment (optional), isUnread (optional), mailboxId (optional), after (optional), before (optional), limit (default: 50)
• get_thread: Get all emails in a conversation thread
  • Parameters: threadId (required)

• get_mailbox_stats: Get statistics for a mailbox (unread count, total emails, etc.)
  • Parameters: mailboxId (optional, defaults to all mailboxes)
• get_account_summary: Get overall account summary with statistics

• bulk_mark_read: Mark multiple emails as read/unread
  • Parameters: emailIds (required array), read (default: true)
• bulk_move: Move multiple emails to a mailbox
  • Parameters: emailIds (required array), targetMailboxId (required)
• bulk_delete: Delete multiple emails (move to trash)
  • Parameters: emailIds (required array)

• list_contacts: List all contacts
  • Parameters: limit (default: 50)
• get_contact: Get a specific contact by ID
  • Parameters: contactId (required)
• search_contacts: Search contacts by name or email
  • Parameters: query (required), limit (default: 20)

• list_calendars: List all calendars
• list_calendar_events: List calendar events
  • Parameters: calendarId (optional), limit (default: 50)
• get_calendar_event: Get a specific calendar event by ID
  • Parameters: eventId (required)
• create_calendar_event: Create a new calendar event
  • Parameters: calendarId (required), title (required), description (optional), start (required, ISO 8601), end (required, ISO 8601), location (optional), participants (optional array)

• list_identities: List sending identities (email addresses that can be used for sending)
• check_function_availability: Check which functions are available based on account permissions (includes setup guidance)
• test_bulk_operations: Safely test bulk operations with dry-run mode
  • Parameters: dryRun (default: true), limit (default: 3)

This server uses the JMAP (JSON Meta Application Protocol) API provided by Fastmail. JMAP is a modern, efficient alternative to IMAP for email access.

Many features in this MCP server are inspired by the official Fastmail JMAP-Samples repository, including:

• Recent emails retrieval (based on top-ten example)
• Email management operations
• Efficient chained JMAP method calls

The server uses bearer token authentication with Fastmail's API. API tokens provide secure access without exposing your main account password.

Fastmail applies rate limits to API requests. The server handles standard rate limiting, but excessive requests may be throttled.

src/
├── index.ts              # Main MCP server implementation
├── auth.ts              # Authentication handling
├── jmap-client.ts       # JMAP client wrapper
└── contacts-calendar.ts # Contacts and calendar extensions

npm run build

npm run dev

MIT

Contributions are welcome! Please ensure that:

1. Code follows the existing style
2. All functions are properly typed
3. Error handling is implemented
4. Documentation is updated for new features

1. Authentication Errors: Ensure your API token is valid and has the necessary permissions
2. Missing Dependencies: Run npm install to ensure all dependencies are installed
3. Build Errors: Check that TypeScript compilation completes without errors using npm run build
4. Calendar/Contacts "Forbidden" Errors: Use check_function_availability to see setup guidance

If calendar and contacts functions return "Forbidden" errors, this is likely due to:

1. Account Plan: Calendar/contacts API may require business/professional Fastmail plans
2. API Token Scope: Your API token may need calendar/contacts permissions enabled
3. Feature Enablement: These features may need explicit activation in your account

Solution: Run check_function_availability for step-by-step setup guidance.

Use the built-in testing tools:

• check_function_availability: See what's available and get setup help
• test_bulk_operations: Safely test bulk operations without making changes

For more detailed error information, check the console output when running the server.

• API tokens are stored encrypted by Claude Desktop when installed via the DXT and are never logged by this server.
• The server avoids logging raw errors and sensitive data (tokens, email addresses, identities, attachment names/blobIds) in error messages.
• Tool responses may include your email metadata/content by design (e.g., listing emails) but internal identifiers and credentials are not disclosed beyond what Fastmail returns for the requested data.
• If you encounter errors, messages are sanitized and summarized to prevent leaking personal information.