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Changelog

All notable changes to Zetian SMTP Server will be documented here.

Upcoming

Version 1.0.10

Initial Release

Core Features

  • High-performance async SMTP server implementation
  • Efficient async/await patterns and optimized I/O
  • Minimal dependencies - only essential packages
  • .NET 6, 7, 8, 9, and 10 support
  • Fluent API with SmtpServerBuilder for easy configuration

Authentication & Security

  • PLAIN and LOGIN authentication mechanisms
  • TLS/SSL support with STARTTLS command
  • Custom authentication providers via IAuthenticator interface
  • Per-IP connection limiting for DDoS protection
  • Certificate validation and secure communication

Message Filtering & Processing

  • IMailboxFilter interface for custom filtering logic
  • DomainMailboxFilter with whitelist/blacklist support
  • CompositeMailboxFilter for combining multiple filters
  • AcceptAllMailboxFilter for development scenarios
  • Rate limiting with configurable thresholds
  • Message size limits and validation

Storage & Persistence

  • IMessageStore interface for custom storage backends
  • FileMessageStore for filesystem persistence
  • NullMessageStore for testing and forwarding scenarios
  • Automatic .eml file generation with headers
  • Directory-based organization by date

SMTP Protocol Support

  • Full SMTP command implementation (HELO, EHLO, MAIL FROM, RCPT TO, DATA, etc.)
  • ESMTP extensions support
  • 8BITMIME for international character support
  • PIPELINING for improved performance
  • SMTPUTF8 for Unicode email addresses
  • SIZE extension with configurable limits

Extensibility & Events

  • Rich event system (SessionCreated, MessageReceived, SessionCompleted, etc.)
  • Extension methods for adding custom functionality
  • Plugin system support via ISmtpPlugin interface
  • Builder pattern extensions (SmtpServerBuilderExtensions)
  • CreateDevelopment() and CreateProduction() helper methods

Developer Experience

  • Comprehensive XML documentation
  • Ready-to-use examples (Basic, Authenticated, CustomProcessing, etc.)
  • Python test scripts for validation
  • Benchmark suite for performance testing
  • Unit test coverage
  • Modern documentation site with Next.js
Planned

Future Releases

Version 1.1.0

  • • DKIM signature validation
  • • SPF record checking
  • • Advanced spam filtering with machine learning
  • • WebSocket support for real-time monitoring

Version 1.2.0

  • • Clustering support for high availability
  • • Redis-based session storage
  • • GraphQL API for management
  • • Advanced metrics and monitoring

Version 2.0.0

  • • Full IMAP server implementation
  • • POP3 server support
  • • Web-based administration panel
  • • Cloud-native deployment templates

Versioning Guidelines

Zetian follows Semantic Versioning 2.0.0 (SemVer)

  • • Major (X.0.0): Breaking API changes
  • • Minor (0.X.0): New features, backwards compatible
  • • Patch (0.0.X): Bug fixes, backwards compatible