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Desktop App

The Papercut SMTP desktop app is both the SMTP server and the viewer — when it's running, you're catching email.

Message Views

Select a message to inspect every layer of it:

  • Message — the rendered HTML, exactly as an email client would show it (embedded images included)
  • Headers — the full header list
  • Body — the plain-text body
  • Sections — every MIME part, viewable and downloadable individually (attachments included)
  • Raw — the raw encoded message source

Right-click works everywhere you'd expect: copy selected text, copy or open links in the HTML view, and Copy / Select All in the Headers, Body, and Raw views.

Rich and Detailed View of Received Email

Notifications & the Tray

New mail triggers a toast notification. Papercut can minimize to the system tray and sit silently until something arrives:

Instant Feedback When New Email Arrives

Configure minimize-to-tray, minimize-on-close, and run-on-startup behavior in Options.

Managing Messages

  • Messages are stored as standard .eml files — right-click → open the containing folder to grab them directly
  • Delete removes the selected message(s); Delete All clears everything older than the moment you confirm
  • Forward a received message on to a real SMTP server (with optional authentication) when you need to get a captured email out

Rules

Papercut can act on messages automatically as they arrive:

  • Forward — pass received messages along to another SMTP server (supports authentication)
  • Relay — conditionally relay matching messages
  • Retention — periodically prune old messages

Configure rules from the main window; if the background service is running, rule and settings changes sync to it automatically.

Options

The gear icon opens Options:

Setting Default Notes
SMTP IP 127.0.0.1 Any accepts mail from other machines
SMTP Port 25 Any free port works
Message folder per-user app data Where .eml files are written
Theme System Light / Dark / follow Windows, with accent color options
Startup — Start with Windows, start minimized

Logs

The Logs view shows the live application log — SMTP server start/stop, connections, received messages, and any errors. It's the first place to look when something seems off (see Troubleshooting).