Release Notes

Papercut SMTP v7.6.2 [2025-11-11]

Release replaces 7.6.1 which had a major issue with email receiving in the UI.

New Features

• Dark Theme Support - Added full dark theme support with automatic Windows dark mode detection and synchronization. Fixes #228 (Thanks, wonea!)
  • System/Light/Dark base theme selection with accent color customization
  • Automatic system dark mode detection with live theme updates
  • AvalonEdit syntax highlighting supports both light and dark modes
  • Theme-aware attachment icons and UI controls throughout the application
• IP Allowlist Support - Added IP allowlist filtering for SMTP and HTTP connections with CIDR notation support. Fixes #333 (Thanks, mhkarimi1383!)
  • Configurable via SmtpServer:AllowedIps setting
  • Support for individual IPs (e.g., 192.168.1.100) and CIDR ranges (e.g., 192.168.1.0/24)
  • Comprehensive unit tests for IP validation and range matching
  • Fail-closed security - blocks all connections if validation fails
• Dynamic Property Editor for Rules - Replaced legacy PropertyGrid with custom MahApps.Metro-compatible dynamic property editor
  • Reflection-based property discovery using System.ComponentModel attributes
  • Intelligent control selection (TextBox, NumericUpDown, ToggleSwitch, PasswordBox)
  • Category-based property organization with smart ordering
  • Resizable GridSplitter between rules list and property editor
  • Full dark theme support in Rules Configuration dialog

Improvements

• .NET 9.0 Upgrade - Upgraded entire solution to .NET 9.0 for improved performance and latest framework features
• Theme Consistency - Modernized UI to use dynamic theming with refreshed Options dialog and message list visuals
• Tab Preservation - Selected message detail tab (Message/Body/Headers/Raw) now preserved when switching between messages
• Code Quality - Fixed numerous compiler warnings and null-safety issues throughout the codebase
• Resource Management - Fixed X509Certificate2Collection resource leak
• Docker Improvements - Updated container and runtime images for .NET 9.0

Code Quality

• Comprehensive unit tests for IP allowlist validation
• More flexible SMTP/server startup wiring and options
• Internal robustness improvements with clearer initialization and lifecycle handling
• Better error handling across core components

Contributors

Special thanks to wonea for requesting dark theme support and mhkarimi1383 for requesting IP allowlist functionality!

Release Notes

Papercut SMTP v7.5.1 [2025-10-31]

Bug Fixes

• Forwarding Rules Failing - Fixed critical bug where email forwarding rules were completely broken due to TaskCanceledException. Fixes #331 (Thanks, wcwhitehead!)
• SSL/TLS Connection Mode - Fixed SSL/TLS connection mode to use SslOnConnect for port 465 and Auto for STARTTLS
• SMTP Timeout - Set proper SMTP timeout of 30 seconds for forwarding rules
• Backend Service Status - Fixed initial status detection for backend service

Contributors

Special thanks to wcwhitehead for reporting the critical forwarding rules bug!

Release Notes

Papercut SMTP v7.5.0 [2025-10-28]

New Features

• Search Functionality - Added Ctrl+F search to all message detail views (Message, Body, Headers, and Raw). Fixes #295
• Zoom Controls - Added Ctrl+Mouse Scroll Wheel zoom support to message detail views with persistence and visual indicators. Fixes #323
• Attachment Display - Attachments now display in the main message panel with icons and easy access. Fixes #112
• Context Menu for Links - Right-click context menu added for email links with copy and open functionality. Fixes #218
• Empty State Placeholders - Added smart empty state messaging to message list and detail views for better first-time user experience. Fixes #268
• SMTP Authentication and TLS/STARTTLS Support - Full support for SMTP authentication and TLS/STARTTLS encryption for secure email testing. Fixes #102
• Periodic Background Rules - Added periodic background rule execution with mail retention cleanup to both UI and Service. Related to #251
• Windows Package Manager (winget) Support - Papercut SMTP can now be installed and updated via winget. Fixes #231
• File Links Support - Made file:/// links functional by opening with shell/explorer. Fixes #232
• Example Console Applications - Added comprehensive example console applications for email testing scenarios
• Installer Help Support - Added help parameter support for PowerShell/cmd users. Fixes #287

Improvements

• Word-Wrap Support - Added CSS word-wrap support to HTML email rendering for better display of long text strings. Fixes #154
• Non-Standard Email Domains - Added support for non-standard email domains in development environments (e.g., .local, .dev). Fixes #284
• SSL Certificate Error Handling - Added optional SSL certificate error handling for WebView2 to support self-signed certificates. Fixes #243
• Comprehensive Unit Tests - Added extensive unit tests with FluentAssertions for improved code quality and reliability
• NuGet Package Upgrades - Upgraded all NuGet packages to latest versions, including migration to new Polly ResiliencePipeline API
• Service Architecture - Refactored attachment and process handling into dedicated services for better separation of concerns
• Settings Debouncing - Implemented debounced settings saves using Rx Throttle operator to reduce unnecessary I/O

Bug Fixes

• Window Size Saving - Fixed window size not saving correctly when minimized. Fixes #327
• PDF Attachment Opening - Fixed PDF attachment opening on Windows 11 24H2 and double-click issues. Fixes #310, #280
• Message Rendering with # Characters - Fixed message rendering for subjects containing # characters. Fixes #282 (Thanks, xavero!)
• SMTP IP Logging - Fixed SMTP service not logging remote client IP address correctly. Fixes #291
• Empty State Flicker - Fixed placeholder flicker when switching between emails
• WebView2 Deserialization - Added robust error handling for WebView2 message deserialization
• Null Safety - Various null safety improvements and fixes throughout the codebase
• Process.Start Null Checks - Added null checks for Process.Start return values to prevent exceptions

Code Quality

• Refactored to use IUiCommandHub.ShowMessage instead of MessageBox.Show for better testability
• Extracted debouncing logic into reusable SettingsSaveDebouncer
• Improved async patterns and error handling in example applications
• Fixed test assertions to use FluentAssertions consistently
• Added nullable reference type attributes throughout codebase

Documentation

• Added comprehensive TLS/STARTTLS setup documentation with Docker examples
• Created example projects: SendEmailTest, SendRichEmailTest, SendWordWrapTest, SendEmailWithTls, SendEmailWithFileLinks
• Improved Docker documentation with troubleshooting guides
• Added installation guide for PowerShell and command-line users

Contributors

Special thanks to xavero for fixing message rendering with # characters!

Upgrading

NOTE: Velopack "Auto-Upgrade" doesn't work before this (v7.0.2) version. You must download the setup and re-run it to upgrade. Once you're on this version, the auto-upgrade system will work!

Release Notes

Papercut SMTP v7.0.2 [2025-10-09]

Improvements

• Modernized versioning system to use Directory.Build.props instead of GlobalAssemblyInfo.cs
• Added Windows ARM64 support (#283)
• Improved port configuration for SMTP and HTTP services (#285, #286, #293)
• Enhanced Docker support with non-privileged ports (SMTP: 2525, HTTP: 8080)
• Consolidated documentation and improved Docker build process

Bug Fixes

• Fixed Windows Service installation and auto-start issues (#294)
• Fixed Linux path separator handling (#292)
• Fixed SMTP server options configuration

Build System

• Refactored build.cake to reduce code duplication
• GitVersion now populates version properties via MSBuild
• Removed deprecated assembly patching approach

Release Notes

Papercut SMTP v7.0.1 [2024-11-08]

• Fixed Run on Startup broken. (Thanks, rikrak))
• Drop service installation mention from README by @Kissaki in #278

Full Changelog: 7.0.0...7.0.1

Release Notes

Papercut SMTP v7.0.0 [2024-10-18]

NOTE: Uninstall any existing Papercut SMTP installations BEFORE installing this new version.

• Upgraded to .NET 8
• Upgraded to latest dependencies (Caliburn Micro, Autofac, MahApps) and associated systems to support .NET 8.
• Switched to Velopack auto-upgradable installation system. Great project! (Thanks, caesay!)
• Fix for log updating constantly causing unnecessary WebView2 loading. (PR thanks to arthurzaczek)
• Fix for double request when clicking on links in emails. Issue #232.
• Added InvokeProcess Rule (#274)

Release Notes

Papercut SMTP 7.0.0 RC1 [2024-06-8]

NOTE: Uninstall any existing Papercut SMTP installations BEFORE installing this new version.

• Upgraded to .NET 8
• Upgraded to latest dependencies (Caliburn Micro, Autofac, MahApps) and associated systems to support .NET 8.
• Switched to Velopack auto-upgradable installation system. Great project! (Thanks, caesay!)
• Fix for log updating constantly causing unnecessary WebView2 loading. (PR thanks to arthurzaczek)

Changes/Fixes:

• Upgraded to .NET Framework v4.8 (PR thanks to 1Jesper1)
• Service doesn't overwrite settings on exit anymore.
• Simplified HTTP binding setting for Service. Basically, "http://0.0.0.0" for "all" binding works again.
• Added Attachment Icon (PR thanks to Cload)
• Added graceful fall-back support and error message if WebView2 isn't properly installed.
• Fix for checking registry key for installing edge webview2 & version fixes (PR thanks to 1Jesper1)

Thank you all for your feedback and assistance with this release!

If you have any problems running Papercut UI, make sure you have installed WebView2. Available here: WebView2 Download

NOTE: Papercut SMTP now requires that Microsoft Edge WebView2 be installed. Papercut SMTP will automatically run the installation dependency if WebView2 is not available.

• Moved to Edge (WebView2) for email display providing modern browser support for viewing.
  • Support for SVGs.
  • Support for newer HTML/CSS display.
• Fixed: Progress bar for Forwarding Dialog displays correctly now.
• Fixed: Multiple issues with the forwarding dialog.
• [#193] Add logging path to settings.json (PR thanks to 1Jesper1)
• [#192] Adds an option (defaulting to true) to enable popup notifications when a new message is received. (PR thanks to richardlawley)
• [#189] Use first capital character in text in "proceed" and "cancel" buttons (PR thanks to 1Jesper1)