Release Notes

Papercut SMTP v7.6.1 [2025-11-08]

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

.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

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

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