MimeKit is a mature, high-performance .NET library for creating, parsing, and manipulating MIME messages (email). It provides comprehensive support for all standard MIME structures (multipart, message/rfc822, content-transfer encodings), internationalized headers (RFC 2047/2231), and email security features including S/MIME, OpenPGP, DKIM, and ARC signing/verification. The library also includes a full HTML5 tokenizer, TNEF (Outlook Transport Neutral Encapsulation Format) reader, text format converters (HTML, flowed, plain), and a stream filter pipeline for encoding/decoding and line-ending normalization. The codebase is well-architected with clean abstractions (visitor pattern, filter chain, encoder/decoder interfaces), extensive unit tests, and benchmarks demonstrating 25x–75x faster parsing than competing .NET MIME libraries. It is distributed as NuGet packages (MimeKit, MimeKitLite) and is a .NET Foundation project. The repository also includes sample applications for Windows Forms, iOS, and Android, and a DKIM verifier sample.

A simple yet rigorously correct .NET library for validating email addresses according to RFC 5322 and Internationalized Email standards (RFC 653x). The core is a hand-written character-by-character parser that rejects invalid syntax while supporting quoted strings, IP literals, international characters, and length constraints per the spec. It provides a static `Validate`/`TryValidate` method and a DataAnnotations `EmailAttribute` for easy integration into ASP.NET or other validation frameworks. The library is well-tested with hundreds of valid and invalid examples, including edge cases like surrogate pairs and maximum-length addresses. It targets multiple .NET frameworks (net462, net8.0, net10.0, netstandard2.0/2.1) and is distributed as a NuGet package with signed assemblies. The code is clean, well-commented, and free of external dependencies for the core validation, making it a trustworthy component for any .NET application needing email input validation.