Mailinator
Disposable email testing inboxes with public and private domains
Open-Source Projects
Discover top open-source software, updated regularly with real-world adoption signals.
Discover top open-source software, updated regularly with real-world adoption signals.
Desktop SMTP server and email viewer for development
Papercut SMTP combines a local SMTP server with an instant email viewer, letting developers safely test application emails without risk of sending to real recipients.
Papercut SMTP solves a critical development problem: testing application emails without the risk of accidentally sending messages to real users. This 2-in-1 tool combines a receive-only SMTP server with a rich desktop email viewer, eliminating the need to configure and maintain separate test mail infrastructure.
Designed for developers building applications or websites that send email, Papercut SMTP captures all outbound messages locally and displays them immediately. View complete email details including HTML rendering, headers, MIME sections, attachments, and raw encoded content. The desktop app runs quietly in the system tray and provides notifications when new messages arrive, accelerating your development cycle.
Available as a Windows desktop application (32-bit and 64-bit installers), an optional background service for always-on email capture, or a Docker container for containerized workflows. The service component includes an HTTP interface accessible at port 8080, enabling team-wide email testing environments. Built with C# and WPF, Papercut SMTP requires Microsoft WebView2 for the desktop UI.
When teams consider Papercut, these hosted platforms usually appear on the same shortlist.
Looking for a hosted option? These are the services engineering teams benchmark against before choosing open source.
Web Application Registration Flow Testing
Developers verify welcome emails, activation links, and HTML rendering without configuring external SMTP servers or risking accidental sends to real addresses.
E-commerce Order Confirmation Debugging
QA teams inspect order confirmation emails, validate dynamic content insertion, and review attachment formatting before production deployment.
Continuous Integration Email Validation
Automated test suites send emails to Dockerized Papercut SMTP instances, enabling programmatic verification of email content and structure in CI/CD pipelines.
Email Template Development and Preview
Designers and developers iterate rapidly on HTML email templates, viewing real-time rendering and MIME structure without waiting for external mail services.
No. Papercut SMTP is a receive-only server designed exclusively for development. It captures emails locally and displays them in the viewer without forwarding to real addresses.
The desktop application runs on Windows (32-bit and 64-bit). It requires Microsoft WebView2. Docker deployment is cross-platform.
Yes. Point your application's SMTP configuration to localhost:25 (or your chosen port). Papercut SMTP accepts standard SMTP connections without authentication requirements.
The desktop app includes the UI and SMTP server. The optional service runs the SMTP server and HTTP interface in the background, capturing emails even when the desktop client isn't running.
Project at a glance
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