mail-mcp

Rust MCP server for Sulkta-hosted email. SMTP send + IMAP read with RFC-correct headers, multipart/alternative when HTML is included, multipart/mixed for attachments, threading via In-Reply-To/References.

Replaces the scripts/kayos_mail.py CLI path that lived in kayos/openclaw-workspace since 2026-04-23.

Why a server, not a CLI

kayos_mail.py shipped without Date or Message-ID headers until a 2026-05-18 patch — exactly the kind of header-discipline regression a typed Rust server prevents at compile time. The "no spam bin" framing is mostly upstream of any client (Rackham postfix + rspamd DKIM-sign at the relay; mail-tester scored 10/10 and port25 SpamAssassin −7.31 on 2026-05-20), but a correct client doesn't trip filters with bad MIME structure, broken threading, or missing headers.

Tools (v0.1)

• mail_send — send mail. Args: account?, to, cc[]?, bcc[]?, subject, body, body_html?, attachments[]?, in_reply_to?, references[]?. Returns {message_id, sent_at}.
• mail_inbox_list — list folder messages newest-first. Args: account?, since? (YYYY-MM-DD), unread_only?, limit? (default 50, max 500), folder? (default INBOX). Uses BODY.PEEK so it does not toggle \Seen.
• mail_inbox_read — fetch one message by UID. Args: account?, uid, folder?, format? (text|html|raw_eml). Attachment payloads are not inlined — only filename/mime_type/size metadata.

Headers we guarantee on outbound

• Date — UTC, RFC 5322 (lettre auto)
• Message-ID — <UUIDv4@<from_addr_domain>> — own-domain, never the container hostname
• From — name <addr>
• MIME-Version: 1.0
• User-Agent: mail-mcp/<version>
• In-Reply-To + References when threading args present
• Content-Type correct for the body shape (text-only / alternative / mixed)

DKIM-Signature is applied by the relay (rspamd on Rackham), not the client.

Build

cargo build --release

Binary lands at target/release/mail-mcp.

Config

mkdir -p ~/.config/mail-mcp
cp config.example.toml ~/.config/mail-mcp/config.toml
chmod 600 ~/.config/mail-mcp/config.toml

Edit accounts as needed. Passwords are NEVER inline:

1. Looked up from the env var named in password_env
2. Falling back to password_file (shell-format: KEY=VALUE per line)
3. Hard-failing with a vault-pointer hint if neither resolves

Vault canonical: bw.sulkta.com → kayos@sulkta.com — IMAP/SMTP.

MCP wiring (Claude Code / kayos-house)

{
  "mcpServers": {
    "mail-mcp": {
      "command": "/usr/local/bin/mail-mcp",
      "args": []
    }
  }
}

Logging is stderr-only — stdout is the JSON-RPC transport.

Future phases

• Phase B (~200 LOC): multi-account routing across all configured [accounts.*], plus mail_thread and mail_search.
• Phase C (~150 LOC): mail_mark (read/unread/flag/trash/archive), mail_attachment_get, mail_reply helper.

Full locked spec: kayos/openclaw-workspace → memory/spec-mail-mcp.md.