Carrier - Rust MCP server for Sulkta email. 10 tools, multi-account, attachment-safe.

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Kayos f7e698b09f smtp: extract validate_send_input + 9 unit tests for size caps Refactor: pull the pre-flight validation block out of send() into a standalone validate_send_input() function. send() now starts with a single validate_send_input(&input)? call. Behavior identical; the extraction is purely so unit tests can exercise the validation paths without standing up a fake SMTP server. New tests (9): - validate_accepts_minimal_input (the happy path) - validate_rejects_empty_to - validate_rejects_too_many_recipients (150 > 100 cap) - validate_recipient_cap_boundary_passes (exactly 100 OK) - validate_rejects_oversized_body - validate_rejects_oversized_body_html - validate_rejects_too_many_attachments - validate_rejects_oversized_attachment_encoded (pre-decode bound) - validate_accepts_at_attachment_boundary Test count: 18 -> 27. All passing.		2026-05-21 08:23:18 -07:00
crates/mail-mcp	smtp: extract validate_send_input + 9 unit tests for size caps	2026-05-21 08:23:18 -07:00
.gitignore	mail-mcp v0.1 — Rust MCP server for Sulkta email	2026-05-21 06:50:25 -07:00
Cargo.lock	mail-mcp v0.1 — Rust MCP server for Sulkta email	2026-05-21 06:50:25 -07:00
Cargo.toml	mail-mcp v0.1 — Rust MCP server for Sulkta email	2026-05-21 06:50:25 -07:00
config.example.toml	mail-mcp v0.1 — Rust MCP server for Sulkta email	2026-05-21 06:50:25 -07:00
README.md	mail-mcp v0.1 — Rust MCP server for Sulkta email	2026-05-21 06:50:25 -07:00

README.md

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:

Looked up from the env var named in password_env
Falling back to password_file (shell-format: KEY=VALUE per line)
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.

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