The Simple Desktop Email Receiver

Papercut SMTP is a 2-in-1 quick email viewer and built-in SMTP server for development. Point your application at localhost:25 and every email it sends is caught, displayed instantly, and never delivered anywhere — body, HTML, headers, attachments, and raw bits included.

Install

Download the desktop installer (always the latest version):

• 64-bit: PapercutSMTP-win-x64-stable-Setup.exe
• 32-bit: PapercutSMTP-win-x86-stable-Setup.exe
• ARM64: PapercutSMTP-win-arm64-stable-Setup.exe

Or via WinGet (may lag behind the latest release):

winget install ChangemakerStudios.Papercut-SMTP

Run it — Papercut is immediately listening on 127.0.0.1:25. Configure your app to send there and you're done.

Docker

docker run -d -p 8080:8080 -p 2525:2525 changemakerstudiosus/papercut-smtp:latest

Web UI at http://localhost:8080, SMTP on localhost:2525. Details on Docker Hub.

MCP Server (AI Agents)

The Papercut Service includes an optional Model Context Protocol server, so AI agents like Claude Code can inspect the email your app sends — list messages, assert on bodies and headers, verify attachment content, and clean up between test runs. Off by default; enable it with the EnableMcpServer setting, then connect:

claude mcp add --transport http papercut http://localhost:8080/mcp

See the MCP Server documentation for setup and the full tool reference.

Documentation

www.papercut-smtp.com — full documentation:

• How It Works — what Papercut is (and isn't), in two minutes
• Getting Started — install, first run, first test email
• Send Email from Your App — copy-paste config for .NET, Node, Python, PHP, Java, Ruby
• Desktop App · Service & Web UI · MCP Server · Docker · TLS & Auth
• Troubleshooting

Release History

See ReleaseNotes.md for the full release history.

Star History

Support Papercut SMTP

Papercut SMTP is free and open source. If it saves you time, consider sponsoring the project — sponsorships go directly toward project costs like the annual code-signing certificate that keeps the installer trusted by Windows.

License

Papercut SMTP is licensed under the Apache License, Version 2.0.