# Natrium Mail

> Sovereign, zero-knowledge, end-to-end encrypted email platform engineered by Natrium Technologies Inc. (https://natrium.sh). Built with AES-256-GCM storage encryption, scrypt + peppered key derivation, FIDO2/WebAuthn hardware passkey authentication, pre-vault attachment threat detonation, and native AI agent protocols (MCP, A2A, WebMCP, OpenAPI 3.1).

## Core Capabilities
- **Zero-Knowledge Encryption**: All emails and attachments are encrypted with AES-256-GCM using unique 96-bit IVs and scrypt key derivation. Plaintext messages and keys are never exposed to third parties.
- **Hardware Passkey & 2FA Identity**: FIDO2/WebAuthn hardware passkeys (YubiKey, Touch ID, Windows Hello) as primary authentication and SecOps governance verification, plus RFC 6238 TOTP 2FA.
- **Threat Isolation Sandbox**: Inbound attachments are screened across 70+ engines (VirusTotal & Hybrid Analysis Falcon Sandbox) prior to vault storage, with automatic 1x1 tracking pixel stripping.
- **Direct MX & Cryptographic Authenticity**: Outbound MTA delivery with 2048-bit RSA DKIM signing, strict SPF, and DMARC alignment.
- **Autonomous Agent Ready**: First-class Model Context Protocol (MCP), Google A2A Agent Cards, W3C WebMCP declarative tools, RFC 9727 API Catalog, and OAuth 2.0 Agent Auth.

## Key Public URLs & Documentation
- [Home & Webmail](https://natrium.sh): Primary webmail interface, account access request, and passkey sign-in gateway.
- [Security Architecture](https://natrium.sh/security): Comprehensive cryptographic whitepaper, threat model, and zero-knowledge storage design.
- [Natrium vs Proton Mail Comparison](https://natrium.sh/compare): Architectural, cryptographic, and privacy comparison between Natrium and Proton Mail.
- [About Natrium Technologies Inc.](https://natrium.sh/about): Corporate mission, zero-knowledge custody philosophy, and sovereign infrastructure.
- [Contact & SecOps](https://natrium.sh/contact): Support (`support@natrium.sh`), vulnerability reporting (`security@natrium.sh`), and direct communication channels.
- [Privacy Policy](https://natrium.sh/privacy): Zero-logs commitment, no third-party trackers, and GDPR/CCPA data minimization policy.
- [Terms of Service](https://natrium.sh/terms): Acceptable use policy, account governance, and service terms.
- [Content Safety & Anti-Abuse Policy](https://natrium.sh/safety): Automated hash screening, zero-tolerance abuse policy, and safety governance.
- [Cookie & Local Storage Policy](https://natrium.sh/cookies): Strictly necessary HMAC-signed session cookie and local WebCrypto storage disclosure.
- [Law Enforcement & Subpoena Guidelines](https://natrium.sh/subpoenas): Statutory requirements (18 U.S.C. § 2703(f) / GDPR Art. 17) and zero-knowledge technical limitations.

## Machine Discovery & Agent Specifications
- [Full LLM Documentation](https://natrium.sh/llms-full.txt): Complete technical documentation of Natrium architecture, cryptographic primitives, and REST APIs.
- [Autonomous Agent Guide (AGENTS.md)](https://natrium.sh/AGENTS.md): Agent interaction rules, available tools, and authentication guide.
- [Autonomous Agent Auth (auth.md)](https://natrium.sh/auth.md): OAuth 2.0, ID-JAG token exchange, and agent registration specification.
- [Service Tiers & Quotas (pricing.md)](https://natrium.sh/pricing.md): Free, Pro, and Enterprise tier specifications, rate limits, and storage quotas.
- [OpenAPI 3.1 Specification](https://natrium.sh/openapi.json): Machine-readable REST API specification with RFC 7807 error schemas.
- [Agents Directory (agents.json)](https://natrium.sh/agents.json): Directory of autonomous AI agent endpoints (`/.well-known/agents.json`).
- [A2A Agent Card](https://natrium.sh/.well-known/agent.json): Google Agent-to-Agent protocol discovery card (`/.well-known/agent-card.json`).
- [MCP Discovery Manifest](https://natrium.sh/.well-known/mcp.json): Model Context Protocol server discovery (`/.well-known/mcp/server-card.json`).
- [WebMCP Tool Manifest](https://natrium.sh/.well-known/webmcp.json): W3C WebMCP declarative tool definitions.
- [RFC 9727 API Catalog](https://natrium.sh/.well-known/api-catalog): Linkset API catalog.
- [AI Catalog](https://natrium.sh/.well-known/ai-catalog.json): Structured AI capability catalog.
- [Agent Skills Index](https://natrium.sh/.well-known/agent-skills/index.json): Advertised agent skill markdown manifests and SHA-256 digests.
- [Web Bot Auth Directory](https://natrium.sh/.well-known/http-message-signatures-directory): Ed25519 JWKS directory for RFC 9421 HTTP Message Signatures.
- [XML Sitemap](https://natrium.sh/sitemap.xml): Complete XML sitemap of public pages and machine-readable specifications.