How to run Papercut SMTP in Docker for continuous testing?

Use the Docker image from Docker Hub with commands like 'docker run -d -p 37408:8080 -p 2525:2525 changemakerstudiosus/papercut-smtp:latest', which sets up the SMTP server on port 2525 and the web interface on 37408. For advanced setups, refer to the Service README for Docker Compose examples and port configurations.

Papercut SMTP or MailHog for email testing in development?

Papercut SMTP excels with its rich desktop GUI, detailed email inspection, and .NET Aspire integration, ideal for Windows-based teams. MailHog is simpler, cross-platform, and better for lightweight, command-line focused testing without a visual interface.

Can Papercut SMTP handle HTML email rendering for testing templates?

Yes, it includes an HTML viewer that displays rendered email templates, as shown in the features screenshot, allowing you to debug design and layout without sending emails to real addresses. This is perfect for verifying template correctness during development.

How to integrate Papercut SMTP with a .NET Aspire project?

Install the NuGet package 'CommunityToolkit.Aspire.Hosting.PapercutSmtp' and configure it in the App Host using builder.AddPapercutSmtp, which automatically assigns ports and exposes a connection string for SMTP client setup. This simplifies local testing in .NET ecosystems.

What are the steps to enable TLS encryption in Papercut SMTP?

Create a self-signed certificate via PowerShell with New-SelfSignedCertificate, then update appsettings.json with CertificateFindType and CertificateFindValue settings, and set the port to 587 for STARTTLS. The README provides detailed examples for both desktop and Docker deployments.

Is Papercut SMTP suitable for testing email attachments in applications?

Yes, it supports viewing and downloading attachments, as demonstrated in the MIME sections view, making it useful for testing file uploads and attachment handling in email-dependent features. You can inspect raw bytes and save files locally.

Open-Awesome

Papercut

Apache-2.0C#7.8.0

A desktop SMTP server and email viewer for safe email testing during development.

GitHub

3.3k stars305 forks0 contributors

What is Papercut?

Papercut SMTP is a desktop application that acts as a local SMTP server and email viewer for development and testing. It captures emails sent from applications during development, preventing them from reaching real recipients while allowing developers to inspect content instantly. It solves the problem of accidental email sends and slow feedback loops in email testing workflows.

Target Audience

Developers and QA engineers who need to test email functionality in applications, websites, or services without risking real email delivery. It's particularly useful for .NET developers using Aspire or anyone working on email-dependent features.

Value Proposition

Developers choose Papercut SMTP because it eliminates the fear of accidental email sends, provides immediate visual feedback, and requires no complex setup. Its integration with Docker, Windows services, and .NET Aspire makes it versatile for various development environments.

Overview

Papercut SMTP -- The Simple Desktop Email Server

Use Cases

Best For

Testing email sending functionality in web applications
Debugging email templates and HTML rendering during development
Preventing accidental email sends to real addresses in test environments
Integrating email testing into .NET Aspire projects
Running a local SMTP server for continuous integration or Docker-based workflows
Inspecting raw email MIME structure and headers for debugging

Not Ideal For

Cross-platform development teams requiring native support for macOS or Linux
Production environments needing real email delivery or integration with external SMTP services
Headless server setups where a GUI is unavailable and only minimal command-line tools are preferred

Pros & Cons

Pros

Instant Email Feedback

Provides real-time notifications when emails are intercepted, as shown in the notification screenshot, allowing developers to quickly verify sends without delays.

Comprehensive Email Inspection

Displays HTML, raw MIME sections, headers, and attachments with detailed views, enabling thorough debugging of email content and structure.

Versatile Deployment Options

Supports desktop, Windows service, and Docker deployments, with specific integration for .NET Aspire projects, making it adaptable to various development workflows.

Security Testing Features

Includes TLS/STARTTLS and SMTP authentication support, configurable via certificates, for testing secure email scenarios in development.

Cons

Windows-Only Desktop Client

The primary desktop application is only available for Windows and requires the WebView2 component, limiting use on other operating systems like macOS or Linux.

Complex TLS Setup

Enabling TLS/STARTTLS requires creating self-signed certificates and editing configuration files, which can be cumbersome for quick testing and adds setup overhead.

Dependency on External Components

Relies on Microsoft WebView2 being installed separately, potentially causing installation issues or compatibility problems on some Windows systems.

Frequently Asked Questions

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