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Changelog

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

Current Release

Version 1.0.20

Full-Featured SMTP Server with Extensions

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

Clustering & High Availability

  • Leader election with Raft consensus algorithm
  • Automatic failover and session migration
  • Load balancing strategies (Round-robin, Least connections, IP Hash)
  • State replication across nodes
  • Multi-region deployment support
  • Maintenance mode with graceful draining

Extensions & Packages

  • Zetian.Relay - SMTP relay with smart host support, queue management, failover
  • Zetian.AntiSpam - SPF/DKIM/DMARC, RBL/DNSBL, Bayesian filtering, Greylisting
  • Zetian.Storage.SqlServer - Enterprise SQL Server storage provider
  • Zetian.Storage.PostgreSql - PostgreSQL with JSONB and partitioning
  • Zetian.Storage.MongoDB - NoSQL storage with GridFS
  • Zetian.Storage.Redis - High-performance in-memory caching
  • Zetian.Storage.S3 - Amazon S3 and compatible object storage
  • Zetian.Storage.AzureBlob - Azure Blob storage with tier management
  • Zetian.HealthCheck - Health monitoring endpoints for Kubernetes/Docker
  • Zetian.Clustering - High availability, load balancing, and state replication

Developer Experience

  • Comprehensive XML documentation
  • 20+ ready-to-use examples including Relay, AntiSpam, Clustering, and Storage providers
  • Python test scripts for validation
  • Benchmark suite for performance testing
  • Comprehensive unit and integration tests
  • Modern documentation site with Next.js and interactive API reference
Planned

Future Releases

Version 1.1.0

  • • WebSocket support for real-time monitoring
  • • Enhanced DMARC/DKIM/SPF reporting and analytics
  • • Advanced queue management with priority routing
  • • Machine learning-based spam detection improvements
  • • AOT compilation support for .NET 8+

Version 1.2.0

  • • GraphQL API for management and monitoring
  • • Enhanced clustering with automatic failover
  • • Distributed message queue improvements
  • • OpenTelemetry integration

Version 2.0.0

  • • Full IMAP server implementation
  • • POP3 server support
  • • Web-based administration dashboard
  • • Cloud-native deployment (Kubernetes, Docker Swarm)
  • • Enterprise single sign-on (SSO) integration
  • • Multi-tenant architecture support

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