Development Windows
Papercut SMTP
Capture development email locally and inspect its HTML, headers, attachments and raw source with Papercut SMTP, a free Windows SMTP server and message viewer.
- Operating system
- Windows 10 or later
- Architecture
- x64
- Download package
- EXE installer
WebView2 Runtime is required for HTML rendering. Separate x86 and ARM64 installers and portable builds are offered by the publisher.
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What is Papercut SMTP?
Papercut SMTP combines a local SMTP server with a desktop inbox for checking email generated by an application. Point your application's SMTP configuration at localhost on port 25, then inspect captured messages without sending them to their intended recipients by default. It suits checking a notification's content, HTML layout or MIME structure during development.
Select a message to switch between rendered HTML, headers, plain-text body, individual MIME sections and raw source. Messages are stored as .eml files, and the desktop interface provides deletion, forwarding, rules and a log view. The default listener is restricted to 127.0.0.1; Options lets you change its address and port.
Local capture is not proof that an email will reach a real inbox. Explicit forwarding or relay rules can send captured messages to another SMTP server, so inspect those settings when you need a capture-only workflow. The standalone desktop receiver must be running to catch mail; the publisher offers a separate service for background reception. Windows 10 or later is required, with WebView2 for HTML rendering. The linked EXE is the x64 installer; x86 and ARM64 packages are separate.
The screenshot is the publisher's v7.0 desktop illustration, not a new capture of version 7.8.0.
What it offers
- Receive application-generated email through a local SMTP server, listening on 127.0.0.1:25 by default.
- Inspect rendered HTML, headers, plain-text body, MIME parts, attachments and raw message source.
- Keep messages as standard .eml files and delete selected messages from the desktop inbox.
- Adjust the listening address, port, storage folder, theme and tray behavior in Options.
- Use explicit forwarding, conditional relay and retention rules when the workflow requires them.
Good to know
- Local capture does not verify real-world delivery to recipients; forwarding and relay settings can send messages outside the local inbox.
- The standalone desktop app must be running to receive messages; background reception uses the separate service.
- Requires Windows 10 or later and WebView2 for HTML email rendering; this download is x64 only.
Product images
Sources
References used for this listing. Retrieval dates do not indicate hands-on testing.
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