SmtpServer

Built entirely in C# with no external dependencies, allowing seamless embedding into .NET applications without foreign code, as highlighted in the README's emphasis on being written for .NET.

Provides IMessageStore, IMailboxFilter, and IUserAuthenticator interfaces for complete control over message handling, filtering, and authentication, enabling custom email workflows.

Supports ESMTP extensions like STARTTLS, AUTH, and SMTPUTF8, ensuring compatibility with contemporary email standards, as listed in the README's feature set.

Leverages the Task Parallel Library for asynchronous operations, enabling scalable and efficient email processing, which is a core claim in the project description.