Connect Fastmail to Claude and ChatGPT
Multi Mail connects Fastmail mailboxes to Claude and ChatGPT with an app password, never your Fastmail password.
For fastmail.com and fastmail.fm addresses, and your own domain at Fastmail.
The AI apps' own connectors
- Fastmail, Fastmail's own connector in Claude's directory, searches, reads, drafts, archives and deletes email in a Fastmail account, beside its calendars, contacts and notes. Read on 3 November 2026.
Connect it
At FastmailNeeds a Fastmail plan that includes app passwords - Basic does not.
The link opens Fastmail in a new tab.
- 1
Sign in at app.fastmail.com and go to Settings, then Privacy & Security.
- 2
In Connected apps & API tokens, click Manage app passwords and access.
- 3
Click New app password, keep Mail, Contacts & Calendars, and click Generate password.
Fastmail shows it once - leave that page open until Lumman asks for it.
Add it to
- 4Add to ClaudeOpens claude.ai - press Connect there.
- 5
Sign in, add your Fastmail mailbox and approve Claude in the window Claude opens - paste the app password when it asks
- 6
Ask Claude about your mail
- 4
Run in Claude Code
/plugin marketplace add lumman-lab/multi-mail/plugin install multi-mail@multi-mailRun the first, then the second.
- 5
Sign in, add your Fastmail mailbox and approve Claude Code on the Lumman page your browser opens - paste the app password when it asks. If none opens, run /mcp and choose multi-mail.
- 6
Ask, or run
/multi-mail:triage
Works fully on ChatGPT Business, Enterprise and Edu.
- 4
Copy the address
- 5Open ChatGPT plugins
Press +, choose Add custom MCP server, name it Multi Mail, paste the address, choose OAuth, tick the box and press Create as a plugin.
- 6
Install it, then sign in, add your Fastmail mailbox and approve on the Lumman page it opens - paste the app password when it asks. In a chat, type @ and choose Multi Mail.
- 4
Add to
~/.cursor/mcp.json - 5
Sign in, add your Fastmail mailbox and approve Cursor on the Lumman page Cursor opens - paste the app password when it asks
Streamable HTTP, OAuth 2.1 with dynamic client registration. No key or client id.
- VS Code
Run MCP: Add Server, choose HTTP, paste the address and name it multi-mail.
- Gemini CLI
gemini extensions install https://github.com/lumman-lab/multi-mailIts first call opens Lumman's sign-in; /mcp auth multi-mail opens it again.
- Antigravity
agy plugin install https://github.com/lumman-lab/multi-mailRun /mcp, open multi-mail_multi-mail and choose Authenticate; approve on the Lumman page, then paste the code Antigravity shows back into it.
Any number of mailboxes. 25 actions a day free, up to 250 a month, 1,000 a day on Standard for $50 a year or $5 a month, or 10,000 a day on Plus for $200 a year or $20 a month.
Reach and limits
- Search and read it together with every other mailbox you add.
- Draft, reply, forward and send from it.
- Archive, bin and file its mail, and clean up its inbox by sender, putting back what a clean-up moved.
- Multi Mail reaches no filters or vacation responder at Fastmail.
If it refuses
- Fastmail refused this password. Use an app password with mail access, on a plan that includes app passwords (Basic does not), and check the address.
- We could not reach Fastmail's mail server. Try again.
Connection
- Receiving
- imap.fastmail.com, port 993
- Sending
- smtp.fastmail.com, port 587
- Login
- Your whole address and the app password
- Check
- Both servers accept the password before the mailbox is added
Your data
- Stored
- The app password, encrypted under a key held outside the database
- No copy kept - read from the mailbox on each call
- Removing it
- Disconnecting deletes our copy of the password, which works until you delete it in Fastmail's settings under Privacy & Security.
Tools
- Offered
- 29 of the 35 - no settings_filters_list, settings_filters_create, settings_filters_update, settings_filters_delete, settings_get_vacation or settings_update_vacation
Everything else
Multi Mail's address, sign-in, limits and every tool: Multi Mail's technical details.