ai-courier 0.5.3

AI-native email & calendar client over JMAP and CalDAV

Courier

AI-native email & calendar client over JMAP and CalDAV.

Your AI agent deserves its own email client — not an adapter wrapping a human one.

The Problem

Every AI agent framework connects to email and calendar by wrapping human-facing apps. MCP servers adapt web UIs. Osascript automates native mail clients. Browser tools click through webmail. Each introduces friction because the agent is fighting an interface designed for someone else.

Courier takes a different approach: connect directly to the open protocols (JMAP for email, CalDAV for calendar) as a first-class client — a peer alongside your human apps, not a wrapper around them.

What Makes It Different

• Context-window-optimized output — emails are structured for AI consumption, not HTML rendering
• Session state & watermarks — "what's new?" is a first-class operation that persists between sessions
• Triage classification — emails arrive pre-sorted: urgent, needs_reply, actionable, fyi, bulk
• Batch-first operations — archive 15 emails in one call, not 15 separate requests
• Sane timezone handling — CalDAV with proper TZID normalization and recurrence expansion
• Composable — higher-order operations like "find all emails from this person and summarize the thread"

Quick Start

pip install ai-courier

# Configure your Fastmail account
courier setup

# Check your inbox (triaged by priority)
courier inbox

# What's new since last check?
courier new

# Today's calendar
courier today

# Find free time
courier free

As an MCP Server

Add to your Claude configuration:

{
  "mcpServers": {
    "courier": {
      "command": "courier-mcp"
    }
  }
}

Available tools:

Tool	Description
email_inbox	Triaged inbox (urgent → bulk)
email_new	New emails since last check (watermark-based)
email_search	Flexible email search
email_sent_since	Recent sent messages (queries Sent mailbox directly)
email_read	Read full email by ID
email_thread	Get full thread
email_thread_digest	Quote-stripped, token-budgeted thread payload
email_archive	Archive emails (batch)
email_trash	Trash emails (batch)
email_mark_read	Mark read (batch)
email_draft	Create draft
email_send	Send email
email_mailboxes	List folders/labels with IDs, paths, roles
email_move	Move emails to a folder (by ID, name, or path)
email_label	Add/remove labels without touching other memberships
email_reply	Threaded reply (In-Reply-To + References); draft or send
email_forward	Forward an email, re-attaches original as .eml; draft or send
calendar_today	Today's events
calendar_week	This week's events
calendar_events	Events in date range
calendar_free	Find free time slots
calendar_create	Create event
calendar_rsvp	Respond to an invite (accepted / tentative / declined)
courier_status	Connection & watermark status

Customizing Triage Rules

Triage rules are defined in YAML. The defaults ship with Courier (see src/courier/default_rules.yaml). To customize, create ~/.config/courier/triage-rules.yaml:

# Force specific senders to a classification (checked first, confidence 1.0)
sender_overrides:
  "[e-mail]": { classification: urgent, reason: "VIP sender" }
  "[e-mail]": { classification: bulk, reason: "always bulk" }

# Custom rules — if you define any, they REPLACE the defaults entirely.
# Omit this section to keep defaults and only add sender overrides.
rules:
  - name: my-custom-rule
    classification: urgent
    confidence: 0.9
    reason: "keyword: '{match}'"
    subject_pattern: "\\b(fire|outage|p0)\\b"

Each rule supports regex match conditions (from_pattern, subject_pattern, body_pattern, domain_pattern) and guard conditions (requires_known_contact, requires_unknown_contact, max_size, requires_thread, requires_flagged). Rules are evaluated top-to-bottom; first match wins.

See src/courier/default_rules.yaml for the full schema documentation and all default rules.

Architecture

AI Agent (Claude, GPT, etc.)
    │
    ▼
Courier MCP Server ← the novel layer
    ├── Email (JMAP)     ├── Calendar (CalDAV)
    │   ├── Watermarks   │   ├── TZID normalization
    │   ├── Triage       │   ├── Recurrence expansion
    │   └── Batch ops    │   └── Free/busy
    └────────────────────┘
    │
    ▼
SQLite (state, watermarks, contact signals)
    │
    ▼
JMAP API ──── CalDAV API
(Fastmail)    (Fastmail)

Courier talks to the same backend your human apps do. It's a parallel client, not a wrapper.

Requirements

• Python 3.11+
• A Fastmail account with an API token (get one here)
• Scopes needed: Mail, Calendars (Contacts optional)

Development

git clone https://github.com/iamdadzilla/courier.git
cd courier
pip install -e ".[dev]"
pytest

Why "Courier"?

A courier delivers messages directly. No intermediary, no adapter, no wrapper. Just the message.

License

MIT