Npubmail MCP Server

npubmail clients

Email for AI agents, owned by a Nostr key. No signup, no password, no API key: the agent's keypair is the account.

This repository holds the open clients for the hosted service at npubmail.com:

• cmd/npubmail: command-line client
• cmd/npubmail-mcp: MCP server (Claude Code, Hermes, OpenClaw, any MCP client)
• client/: Go library (EnsureMailbox, CreateAlias, WaitFor, Send, ...)
• skills/npubmail/SKILL.md: agent skill
• docs/: HTTP API, the sealed-mail format (SEAL.md) with test vectors, and Python/JS examples

Install

One click (Claude Desktop and other MCPB clients): download npubmail-mcp-0.2.0.mcpb and open it.

Listed in the official MCP Registry as com.npubmail/npubmail.

curl -fsSL https://npubmail.com/install | sh       # prebuilt, checksummed binaries
# or from source:
go install github.com/obvioussummer46/npubmail/cmd/npubmail-mcp@latest
go install github.com/obvioussummer46/npubmail/cmd/npubmail@latest

MCP config:

mcp_servers:
  npubmail:
    command: npubmail-mcp          # talks to https://npubmail.com
    timeout: 660                   # wait_for_* can block up to 600 s

Use it

npubmail init myagent                      # -> myagent@npubmail.com (key at ~/.config/npubmail/nsec)
npubmail alias --from github.com --ttl 24  # disposable, sender-locked address
npubmail code --timeout 120                # block until mail arrives, print the OTP

Agents: start at https://npubmail.com/llms.txt.

What the service does

• Receive: free. Disposable aliases per signup, codes and links extracted.
• Encrypted at rest: each message is sealed to the owner's Nostr key (see docs/SEAL.md); the server cannot read stored mail.
• Send: replies to people who wrote to you are free, and so is mail to other npubmail mailboxes. Mailing a new recipient costs a few sats over Lightning, per message, with no account balance.
• Inbound TLS (STARTTLS), DKIM/SPF/DMARC on outbound.

Your key is your account

~/.config/npubmail/nsec is the only credential. Back it up; there is no reset. The clients sign every request locally (NIP-98) and never send the key anywhere.

Licence

MIT (LICENSE): clients, library, protocol packages, skill and examples. The server is not in this repository.