Why Nuncio Exists.
Email rebuilt for today — private, fast, secure, and AI-integrated without giving up control of your data, your privacy, or your flow.
Breaking Away From Walled Gardens
For over a decade, personal and enterprise communication has been fractured across paid cloud subscriptions, closed proprietary formats, locked-away data silos, and compromised user experiences depending on whether you're on a Mac, Windows PC, Linux terminal, or mobile device.
Nuncio was built to eliminate those trade-offs. Created by James Maes (KofTwentyTwo), Nuncio gives developers, power users, and AI agents total speed, complete sovereign data ownership, zero-trust encryption, and sane AI integration.
1. Sane & Controlled AI / LLM Access
AI co-pilots should empower you, not exfiltrate your life. Nuncio's McpAgentPolicy enforces granular RBAC capability flags (read_mail, send_mail, read_calendar), folder access boundaries, and automatic SSN/credit card redaction before any payload touches an LLM context window.
2. First-Class UI/UX in Every Space
No second-class interfaces. Enjoy equal polish across native macOS glassmorphism, Windows, Linux, Vim Ratatui Terminal TUI, POSIX scriptable CLI, and native MCP AI agent integration with 100% feature parity.
3. Uncompromising Speed & Performance
Engineered in native Rust over single-writer SQLite WAL storage. Search 100,000+ emails in under 10 milliseconds, execute NSQL rules in microsecond time, and run with zero battery drain.
4. Sovereign Control & Zero Closed Formats
No cloud lock-in, no proprietary sync servers, no closed formats. Your emails, accounts, rules, and calendars stay in standard local SQLite files on your disk. You own your data 100%.
5. Zero-Trust Security & Encryption
Column-level AES-256-GCM data-at-rest encryption (PayloadCipher), age X25519 attachment ciphers, ZeroizeOnDrop memory page locking, and HTML email sandboxing with tracking pixel neutralization.
6. WORM Cryptographic Audits & Immutability
Every automated rule match, webhook dispatch, account mutation, and AI MCP tool call is recorded in an immutable Write Once Read Many (WORM) audit ledger sealed with HMAC-SHA256 hash chains.
Open-Source Ecosystem & Author Credits
Nuncio is made possible by the incredible open-source Rust, Web, Security, and Protocol communities. We extend our deepest gratitude to the authors and maintainers of these projects. Click any author or repository below to visit their official profiles.
Rust Core Systems & Data Storage
Async, pure-Rust SQL engine powering type-safe SQLite database operations and migrations.
Pure Rust SQL lexer and parser engine powering the Nuncio SQL Filter Language (NSQL) compiler.
Event-driven asynchronous Rust runtime driving background IMAP IDLE, JMAP push, and IPC streaming.
Generic serialization/deserialization framework powering data models across all crates.
Ergonomic, type-safe Rust error handling and domain error mappings.
Mail Protocols & Parsing Engines
Asynchronous IMAP client library driving real-time TLS 993 inbox synchronization.
Modern Rust SMTP email client delivering outbound TLS 587/465 message transport.
High-performance MIME parser for raw RFC 5322 emails, headers, and attachment boundaries.
Converting HTML email markup to clean, un-tracked ANSI terminal text and Markdown.
Security, Cryptography & Vault Enclaves
Safe, fast, small crypto primitives in Rust and C for cryptographic operations.
Pure Rust AES-GCM authenticated encryption powering column-level PayloadCipher.
Modern X25519 file and stream encryption format powering large binary attachment ciphers.
Secure memory page zeroing (ZeroizeOnDrop) preventing key material leakages in RAM buffers.
Native OS credential manager integration (Windows DPAPI, macOS Keychain Access, Linux Secret Service).
Cryptographic HMAC-SHA256 hash-chain calculation for WORM audit ledgers.
Presentation Shells & UI Frameworks
Lightweight, secure desktop application framework driving the Glassmorphic GUI.
Terminal user interface framework powering the Vim-fueled Ratatui TUI.
Declarative command-line argument parser powering the POSIX scriptable CLI (nuncio-cli).
React web framework powering nuncio-website with static site generation and Turbopack.
Utility-first CSS engine powering responsive modern styling across website components.
Clean, modern open-source icon suite across Next.js and Tauri interfaces.
Open Protocols & Standards
Open stdio JSON-RPC 2.0 standard connecting AI agents (Claude, Antigravity, Cursor) directly to Nuncio tools.
Universal open standards for portable email archiving, export, and transport.
Proof Key for Code Exchange protocol driving secure credential-free Google Workspace authentication.