Protonmail MCP Server

The Protonmail MCP server solves a common pain point for developers building AI‑powered applications: sending secure, encrypted emails directly from an assistant without exposing user credentials or handling SMTP logic manually. By integrating Protonmail’s robust, privacy‑first SMTP service into the Model Context Protocol (MCP) ecosystem, this server lets Claude Desktop and the Cline VSCode extension issue emails on a user’s behalf using their own Protonmail account. The result is a seamless, secure channel for notifications, alerts, or user‑generated content to be delivered via email without requiring additional third‑party services.

At its core, the server exposes a single tool—. The assistant can invoke this tool with parameters such as recipients, subject, body, and optional CC/BCC fields. The server handles all SMTP details: establishing a connection to (or a custom host), negotiating TLS or SSL, authenticating with the user’s SMTP password, and sending the message in either plain text or HTML format. Comprehensive error handling ensures that failures (authentication errors, network timeouts, or SMTP rejections) are reported back to the assistant in a readable form, allowing for graceful retries or user prompts.

Key capabilities include:

• Multi‑recipient support: Accept comma‑separated lists for , , and .
• HTML rendering: Toggle to send rich‑text emails.
• Robust logging: Debug mode captures detailed SMTP exchanges, useful for troubleshooting firewall or account restrictions.
• Cross‑platform compatibility: The same configuration works in both the standalone Claude Desktop app and the VSCode Cline extension, thanks to MCP’s unified protocol.

Typical use cases are abundant in developer workflows. For example, a coding assistant can automatically email code snippets or debugging reports to a user’s inbox; an AI‑driven ticketing system can notify stakeholders of status changes; or a CI/CD pipeline integrated with Claude could send build logs directly via Protonmail. Because the server operates locally on the user’s machine, it preserves end‑to‑end encryption and avoids exposing credentials to external servers.

The integration process is straightforward: developers set environment variables in each client’s configuration file (username, SMTP password, host, port, security flag), then call the tool from within a prompt. The assistant’s natural language instructions are translated into MCP calls, the server executes the SMTP transaction, and any response or error is returned to the assistant for further action. This tight coupling between AI logic and secure email delivery makes Protonmail MCP a powerful addition to any privacy‑conscious, automation‑heavy development stack.