Protonmail-rs - Proton Mail MCP Server¶

Unofficial, pure-Rust Proton Mail client - library, CLI, and MCP server with end-to-end OpenPGP encryption. Gives AI agents secure, encrypted email capabilities through Switzerland's privacy-first email provider.

Detail	Value
GitHub	filippofinke/protonmail-rs
Language	Rust
Tools	MCP-native email operations
Transport	stdio
Stars	★1 (new - July 2026)
License	TBD

Why This Matters for Operators¶

Proton Mail is the leading encrypted email provider, used by 100M+ users worldwide - including journalists, legal firms, healthcare providers, and security-conscious businesses. This MCP server is the first to bring Proton Mail's end-to-end encryption to AI agent workflows:

HIPAA/GDPR compliance: Encrypted email for regulated industries
Legal communications: Attorney-client privileged email through AI agents
Secure client onboarding: AI agents send encrypted onboarding documents
Privacy-first operations: Zero-access encryption means not even Proton can read emails

Prerequisites¶

Proton Mail account (free or paid)
Proton Mail Bridge (for IMAP/SMTP access - paid plans only)
Rust toolchain (for building from source)
OpenPGP keys managed through Proton's key infrastructure

Installation¶

# Clone and build
git clone https://github.com/filippofinke/protonmail-rs.git
cd protonmail-rs
cargo build --release

# Binary at target/release/protonmail-rs

MCP Client Configuration¶

{
  "mcpServers": {
    "protonmail": {
      "command": "/path/to/protonmail-rs",
      "args": ["mcp"],
      "env": {
        "PROTON_API_URL": "https://mail.proton.me/api",
        "PROTON_SESSION_KEY": "your-session-key"
      }
    }
  }
}

Key Capabilities¶

Capability	Description
Read inbox	Fetch and decrypt emails with OpenPGP
Send encrypted	Compose and send end-to-end encrypted emails
Search	Search encrypted mailbox by subject, sender, date
Key management	Import/export PGP keys, verify signatures
Folder operations	List, create, move emails between folders
Labels & filters	Apply labels and manage sieve filters

CorpusIQ Use Case¶

Operators in regulated industries can use this MCP server alongside CorpusIQ's business connectors:

Secure document workflow: AI agent sends encrypted contracts (via Proton Mail) when DocuSign events complete
Compliance notifications: Agent sends encrypted audit logs to compliance officers
Client communications: Agent manages encrypted email threads for legal/financial clients
Privacy-first CRM: Combine with HubSpot connector for encrypted client communications

Security Considerations¶

End-to-end encryption: Emails are encrypted client-side before transmission - the MCP server never sees plaintext
Zero-access architecture: Proton Mail cannot decrypt your emails
Session management: Use short-lived session tokens, not persistent credentials
Audit trail: All agent-initiated email operations are logged in Proton Mail's activity log

Integration with CorpusIQ¶

CorpusIQ is the connector layer that lets AI assistants read the systems a business already runs on - accounting, payments, CRM, email, files and analytics - and answer with the source named. It is read-only by design: it retrieves data and never writes to, or acts in, a connected system, which is what makes it safe to point at live accounts.

This page is part of the CorpusIQ directory, the reference we maintain for the MCP server and agent-skill ecosystem. Run alongside CorpusIQ, a third-party server like this one can be combined with a company's own business data in a single answer.

See what CorpusIQ connects

Limitations¶

Proton Mail Bridge required for IMAP/SMTP access (paid plans only, ~$4/month)
Unofficial client - not maintained by Proton AG
New project (July 2026) - expect API changes and limited tool coverage initially
SRP authentication may require periodic re-authentication

Troubleshooting¶

Issue	Solution
`Authentication failed`	Regenerate session key via Proton web client → Settings → Security → Sessions
`OpenPGP key not found`	Verify key is uploaded to Proton's key server and public key is accessible
`Rate limited`	Proton Mail has per-account rate limits (~100 emails/day free, higher on paid)
`Build fails`	Ensure Rust toolchain is up to date: `rustup update stable`

Discovered: July 1, 2026 · Source: GitHub (topic:mcp-server created >2026-06-30) Part of the CorpusIQ External MCP Server Catalog