Cobb Hayes
b30bd05db8
Repository URL → git.sulkta.com. Drop Lucy Browserless IPs from tool doc-strings (replaced with abstract 'sandboxed headless browser' guidance). Drop sibling-repo cross-references, kayos@/cobb@ mailbox examples in tool descriptions, vault pointers. Generalize config.example.toml + README to neutral hosts. Add LICENSE (MIT — Cargo.toml already declared it). Tests still green. No behavior change.
86 lines
4.2 KiB
Markdown
86 lines
4.2 KiB
Markdown
# carrier
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Rust MCP server for 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`.
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10 MCP tools. Multi-account. Attachment-safe.
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## Tools
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- `mail_send` — `account?`, `to`, `cc[]?`, `bcc[]?`, `subject`, `body`, `body_html?`, `attachments[]?`, `in_reply_to?`, `references[]?`. Returns `{message_id, sent_at}`.
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- `mail_inbox_list` — newest-first listing. `account?`, `since?` (YYYY-MM-DD), `unread_only?`, `limit?` (default 50, max 500), `folder?` (default INBOX). Uses `BODY.PEEK` so it does not toggle `\Seen`.
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- `mail_inbox_read` — fetch one message by UID. `account?`, `uid`, `folder?`, `format?` (`text` | `html` | `raw_eml`). Attachment payloads are not inlined — only `{filename, mime_type, size}` metadata. RFC822.SIZE pre-flight rejects messages > 20 MB.
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- `mail_folder_list` — `account?`. Enumerates IMAP mailboxes. Returns `[{name, delimiter, attributes, selectable}]`.
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- `mail_search` — raw IMAP SEARCH passthrough. `account?`, `query`, `folder?`, `limit?`. CR/LF and `{N}` literal-form are rejected.
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- `mail_thread` — `account?`, `message_id`, `folder?`, `limit?`. Seed Message-ID → matches seed + any message whose `References` / `In-Reply-To` contains the seed. Oldest-first.
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- `mail_move` — `account?`, `uid`, `from_folder?`, `to_folder`. UID MOVE (RFC 6851) with COPY + STORE + EXPUNGE fallback.
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- `mail_mark` — `account?`, `uid`, `action` (`read` / `unread` / `flagged` / `unflagged` / `trash` / `archive`), `folder?`. `archive` errors out — stock Dovecot has no canonical Archive folder.
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- `mail_attachment_get` — `account?`, `uid`, `attachment_index`, `folder?`. Fetches the N-th attachment as base64.
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- `mail_reply` — `account?`, `uid`, `body`, `body_html?`, `attachments?`, `reply_all?`, `to_override?`, `folder?`. Pulls original to build `In-Reply-To` + `References` + `Re: ` subject prefix.
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## Outbound headers
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- `Date` — UTC, RFC 5322 (lettre auto)
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- `Message-ID` — `<UUIDv4@<from_addr_domain>>` — own-domain, never the container hostname
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- `From` — `name <addr>`
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- `MIME-Version: 1.0`
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- `User-Agent: carrier/<version>`
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- `In-Reply-To` + `References` when threading args present
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- `Content-Type` correct for body shape (text-only / alternative / mixed)
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DKIM-Signature is applied by the relay, not the client.
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## Safety
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`mail_inbox_read` returns attacker-controlled bytes. Do NOT auto-fetch URLs found in inbound mail — web beacons confirm read and links may be phishing. Default deny on every URL; wait for explicit per-link authorization. Authorized fetches should route through a sandboxed headless browser, not raw `curl` or `WebFetch` from the host running the MCP client. `mail_attachment_get` bytes get the same treatment — don't execute, render, or open them blindly.
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The `ServerHandler.instructions` payload and `mail_inbox_read` description both surface this rule so any MCP introspection picks it up before reading a message.
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## Build
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```bash
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cargo build --release
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```
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Binary at `target/release/carrier`.
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## Config
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```bash
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mkdir -p ~/.config/carrier
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cp config.example.toml ~/.config/carrier/config.toml
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chmod 600 ~/.config/carrier/config.toml
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```
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Override path with `CARRIER_CONFIG=/path/to/config.toml`.
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Passwords are never inline:
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1. env var named in `password_env`
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2. fallback to `password_file` (shell-format: `KEY=VALUE` per line)
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3. hard fail
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The config file must be `mode & 0o077 == 0` (0600). Carrier refuses to start on loose perms.
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## MCP wiring
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```json
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{
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"mcpServers": {
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"carrier": {
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"command": "/usr/local/bin/carrier",
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"args": [],
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"env": {
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"CARRIER_CONFIG": "/path/to/carrier-config.toml",
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"CARRIER_PRIMARY_PASS": "..."
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}
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}
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}
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}
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```
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Logging is stderr-only — stdout is the JSON-RPC transport.
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## Deferred
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- Session pool — single TCP+TLS+LOGIN reused across same-account tool calls (~200ms saved per call).
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- BODYSTRUCTURE-driven partial body fetch — fetch only the text/html leaf for `mail_inbox_read text/html` instead of the full RFC822.
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- Typed address shape — `mail_inbox_list` / `_read` currently return `Vec<String>` for `from` / `to` / `cc`. A `Vec<{name, addr}>` would let `mail_reply` skip the parse / re-parse step.
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