base on smtp4dev - the fake smtp email server for development and testing # <img src='Rnwood.Smtp4dev/ClientApp/public/logo.png' alt='logo'/> **smtp4dev - the fake SMTP email server for development and testing.** A dummy SMTP server for Windows, Linux, Mac OS-X (and maybe elsewhere where .NET Core is available). Lets you test your application without spamming your real customers. smtp4dev support many advanced features: - OpenAPI/Swagger API - IMAP access to retrieve and delete messages - SMTP session logging - UTF8 support - Viewport size switcher to simulate mobile etc - Multipart MIME inspector - HTML compatibility report and HTML validation - TLS/SSL with implicit and STARTTLS modes and auto self-signed cert generation - Authentication - Multiple mailboxes along with rules to control what message goes where - Reply, compose and relay messages including rules to auto relay - Scripting expressions including error simulation *If you're looking for the older v2 Windows only GUI version. [Grab it here](https://github.com/rnwood/smtp4dev/releases/tag/v2.0.10).* ## How smtp4dev Compares There are several fake SMTP servers available for development and testing. Here's how smtp4dev stacks up against other popular options: | Feature | smtp4dev | MailHog¹ | MailCatcher² | MailDev³ | FakeSMTP⁴ | |---------|----------|----------|-------------|---------|-----------| | **Web Interface** | ✅ Advanced | ✅ Basic | ✅ Basic | ✅ Basic | ❌ Desktop GUI | | **SMTP Server** | ✅ | ✅ | ✅ | ✅ | ✅ | | **IMAP Server** | ✅ | ❌ | ❌ | ❌ | ❌ | | **API (REST/OpenAPI)** | ✅ Swagger docs | ✅ Basic⁵ | ✅ RESTful⁶ | ✅ Basic⁷ | ❌ | | **HTML Email Rendering** | ✅ Advanced | ✅ Basic | ✅ Basic | ✅ Basic | ❌ | | **HTML Compatibility Reports** | ✅ | ❌ | ❌ | ❌ | ❌ | | **Responsive Email Testing** | ✅ Viewport switcher | ❌ | ❌ | ✅ Resizable⁸ | ❌ | | **MIME Parts Inspector** | ✅ | ❌ | ❌ | ❌ | ❌ | | **SMTP Session Logging** | ✅ Detailed | ❌ | ❌ | ❌ | ❌ | | **TLS/SSL Support** | ✅ Auto-cert generation | ❌ | ❌ | ✅ Basic⁹ | ❌ | | **Authentication** | ✅ | ✅ Basic¹⁰ | ❌ | ✅ Basic¹¹ | ❌ | | **Multiple Mailboxes** | ✅ With rules | ❌ | ❌ | ❌ | ❌ | | **Message Relay** | ✅ With rules | ✅ Basic¹² | ❌ | ✅ Basic¹³ | ❌ | | **Message Composition** | ✅ | ❌ | ❌ | ❌ | ❌ | | **Scripting & Error Simulation** | ✅ | ✅ Limited¹⁴ | ❌ | ❌ | ❌ | | **Dark Mode** | ✅ | ❌ | ❌ | ❌ | ❌ | | **Cross-Platform** | ✅ .NET 8 | ✅ Go | ✅ Ruby | ✅ Node.js | ✅ Java | | **Docker Support** | ✅ | ✅ | ✅ | ✅ | ❌ | ### Sources 1. [MailHog GitHub Repository](https://github.com/mailhog/MailHog) - Features verified from official documentation 2. [MailCatcher GitHub Repository](https://github.com/sj26/mailcatcher) - Features verified from official documentation 3. [MailDev GitHub Repository](https://github.com/maildev/maildev) - Features verified from official documentation 4. [FakeSMTP GitHub Repository](https://github.com/Nilhcem/FakeSMTP) - Features verified from official documentation 5. MailHog API: [APIv1](https://github.com/mailhog/MailHog/blob/master/docs/APIv1.md) and [APIv2](https://github.com/mailhog/MailHog/blob/master/docs/APIv2.md) documentation 6. MailCatcher API: RESTful URLs documented in [README](https://github.com/sj26/mailcatcher#api) but no formal API documentation 7. MailDev API: [REST API documentation](https://github.com/maildev/maildev/blob/master/docs/rest.md) 8. MailDev responsive testing: ["Test responsive emails with resizable preview pane"](https://github.com/maildev/maildev#features) 9. MailDev TLS/SSL: [SSL options documented](https://github.com/maildev/maildev#usage) (`--incoming-secure`, `--incoming-cert`, `--incoming-key`) 10. MailHog authentication: [HTTP basic authentication](https://github.com/mailhog/MailHog/blob/master/docs/Auth.md) for UI and API 11. MailDev authentication: [Authentication options](https://github.com/maildev/maildev#usage) (`--incoming-user/pass`, `--web-user/pass`) 12. MailHog relay: ["Release messages to real SMTP servers"](https://github.com/mailhog/MailHog#features) 13. MailDev relay: ["Ability to relay email to an upstream SMTP server"](https://github.com/maildev/maildev#features) with auto-relay mode 14. MailHog scripting: [Chaos Monkey for failure testing](https://github.com/mailhog/MailHog/blob/master/docs/JIM.md) ### Why Choose smtp4dev? **For Advanced Development & Testing**: If you need comprehensive email testing capabilities, smtp4dev offers features not found in other tools like HTML compatibility analysis, responsive design testing, and detailed SMTP session logging. **For Production-Like Testing**: With IMAP support, TLS/SSL, authentication, and multiple mailboxes, smtp4dev can simulate real email server behavior more accurately. **For Team Workflows**: The advanced web interface, API documentation, and message relay capabilities make smtp4dev ideal for development teams and CI/CD pipelines. **For Modern Email Development**: Responsive email testing, HTML validation, and compatibility reports help ensure your emails work across all clients and devices. > <a style="float: right" href="https://www.patreon.com/bePatron?u=38204828" data-patreon-widget-type="become-patron-button"><img alt='Become a Patreon' src='https://c5.patreon.com/external/logo/become_a_patron_button.png' height="30px"></a> <a style="float: right" href='https://www.paypal.me/rnwood'><img alt='Donate' src='https://www.paypalobjects.com/webstatic/en_US/btn/btn_donate_pp_142x27.png'/></a> *If you find smtp4dev useful, please consider supporting further development by making a donation* > . ## Getting Started [Installation Instructions](docs/Installation.md) [Configuration](docs/Configuration.md) [Configuring your programs to send mails to smtp4dev](docs/Configuring-Clients.md) [API](docs/API.md) [📚 **View Full Documentation**](docs/README.md) ## Security **⚠️ Docker Users**: Please read [Docker Security Guidelines](docs/Docker-Security.md) to prevent accidental public exposure of your smtp4dev instance to the world! ## Screenshots ### Main Message Interface The main interface showing received emails with sender, recipient, subject, and timestamps.  ### HTML Email Rendering & Viewport Simulation View HTML emails with rich formatting, including viewport size simulation for testing responsive email designs.  ### HTML Compatibility Analysis Comprehensive email client compatibility reports showing which HTML/CSS features are supported across different email clients.  ### Message Source & Raw Content Inspect the raw message source with syntax highlighting and line numbers for debugging.  ### SMTP Session Logging View detailed SMTP session logs to debug email delivery issues and protocol interactions.  ### MIME Parts Inspector Analyze multipart emails with attachments using the built-in MIME inspector.  ### Dark Mode Support Full dark mode support for comfortable viewing in low-light environments.  [](https://app.fossa.com/projects/git%2Bgithub.com%2Frnwood%2Fsmtp4dev?ref=badge_shield) ## Contributing We welcome contributions! Before submitting a pull request, please: 1. Read our [Contributing Guide](CONTRIBUTING.md) 2. Sign the [Contributor License Agreement](CLA.md) ## License [](https://app.fossa.com/projects/git%2Bgithub.com%2Frnwood%2Fsmtp4dev?ref=badge_large) ", Assign "at most 3 tags" to the expected json: {"id":"6617","tags":[]} "only from the tags list I provide: [{"id":77,"name":"3d"},{"id":89,"name":"agent"},{"id":17,"name":"ai"},{"id":54,"name":"algorithm"},{"id":24,"name":"api"},{"id":44,"name":"authentication"},{"id":3,"name":"aws"},{"id":27,"name":"backend"},{"id":60,"name":"benchmark"},{"id":72,"name":"best-practices"},{"id":39,"name":"bitcoin"},{"id":37,"name":"blockchain"},{"id":1,"name":"blog"},{"id":45,"name":"bundler"},{"id":58,"name":"cache"},{"id":21,"name":"chat"},{"id":49,"name":"cicd"},{"id":4,"name":"cli"},{"id":64,"name":"cloud-native"},{"id":48,"name":"cms"},{"id":61,"name":"compiler"},{"id":68,"name":"containerization"},{"id":92,"name":"crm"},{"id":34,"name":"data"},{"id":47,"name":"database"},{"id":8,"name":"declarative-gui "},{"id":9,"name":"deploy-tool"},{"id":53,"name":"desktop-app"},{"id":6,"name":"dev-exp-lib"},{"id":59,"name":"dev-tool"},{"id":13,"name":"ecommerce"},{"id":26,"name":"editor"},{"id":66,"name":"emulator"},{"id":62,"name":"filesystem"},{"id":80,"name":"finance"},{"id":15,"name":"firmware"},{"id":73,"name":"for-fun"},{"id":2,"name":"framework"},{"id":11,"name":"frontend"},{"id":22,"name":"game"},{"id":81,"name":"game-engine "},{"id":23,"name":"graphql"},{"id":84,"name":"gui"},{"id":91,"name":"http"},{"id":5,"name":"http-client"},{"id":51,"name":"iac"},{"id":30,"name":"ide"},{"id":78,"name":"iot"},{"id":40,"name":"json"},{"id":83,"name":"julian"},{"id":38,"name":"k8s"},{"id":31,"name":"language"},{"id":10,"name":"learning-resource"},{"id":33,"name":"lib"},{"id":41,"name":"linter"},{"id":28,"name":"lms"},{"id":16,"name":"logging"},{"id":76,"name":"low-code"},{"id":90,"name":"message-queue"},{"id":42,"name":"mobile-app"},{"id":18,"name":"monitoring"},{"id":36,"name":"networking"},{"id":7,"name":"node-version"},{"id":55,"name":"nosql"},{"id":57,"name":"observability"},{"id":46,"name":"orm"},{"id":52,"name":"os"},{"id":14,"name":"parser"},{"id":74,"name":"react"},{"id":82,"name":"real-time"},{"id":56,"name":"robot"},{"id":65,"name":"runtime"},{"id":32,"name":"sdk"},{"id":71,"name":"search"},{"id":63,"name":"secrets"},{"id":25,"name":"security"},{"id":85,"name":"server"},{"id":86,"name":"serverless"},{"id":70,"name":"storage"},{"id":75,"name":"system-design"},{"id":79,"name":"terminal"},{"id":29,"name":"testing"},{"id":12,"name":"ui"},{"id":50,"name":"ux"},{"id":88,"name":"video"},{"id":20,"name":"web-app"},{"id":35,"name":"web-server"},{"id":43,"name":"webassembly"},{"id":69,"name":"workflow"},{"id":87,"name":"yaml"}]" returns me the "expected json"