Zetian — nugetz

using Zetian.Models;
using Zetian.Server;

var server = new SmtpServerBuilder()
    .Port(587)
    .ServerName("My SMTP Server")
    .MaxMessageSizeMB(25)
    .MaxConnections(50)
    .RequireAuthentication()
    .AuthenticationHandler(async (user, pass) =>
    {
        // Custom authentication logic
        return await ValidateUser(user, pass)
            ? AuthenticationResult.Succeed(user)
            : AuthenticationResult.Fail();
    })
    // New features
    .EnableSmtpUtf8()
    .WithFileMessageStore(@"C:\smtp_messages")  // Protocol-level storage
    .WithSenderDomainWhitelist("trusted1.com", "trusted2.com")  // Protocol-level filtering
    .WithSenderDomainBlacklist("spam.com", "junk.org")
    .Build();

// Save messages to file system with date structure (Protocol-level)
using Zetian.Server;
using Zetian.Extensions;

var server = new SmtpServerBuilder()
    .Port(25)
    .WithFileMessageStore(@"C:\mail", createDateFolders: true)  // Saves at protocol level
    .Build();

// Or use the extension method (Event-based)
server.SaveMessagesToDirectory(@"C:\mail");  // Saves via event handler

// Or use custom message store
using Zetian.Server;
using Zetian.Abstractions;

public class MongoMessageStore : IMessageStore
{
    public async Task<bool> SaveAsync(ISmtpSession session, ISmtpMessage message, CancellationToken cancellationToken)
    {
        // Save to MongoDB
        return true;
    }
}

var server = new SmtpServerBuilder()
    .MessageStore(new MongoMessageStore())
    .Build();

// Protocol-level domain filtering (rejects at SMTP command level)
using Zetian.Server;
using Zetian.Extensions;

var server = new SmtpServerBuilder()
    .WithSenderDomainWhitelist("company.com", "partner.com")
    .WithRecipientDomainWhitelist("mydomain.com")
    .WithSenderDomainBlacklist("spam.com")
    .Build();

// Event-based domain filtering (filters after message received)
server.AddAllowedDomains("example.com");  // Extension method
server.AddSpamFilter(new[] { "spam.com" });  // Extension method

// Custom mailbox filter
using Zetian.Server;
using Zetian.Abstractions;

public class CustomMailboxFilter : IMailboxFilter
{
    public async Task<bool> CanAcceptFromAsync(ISmtpSession session, string from, long size, CancellationToken cancellationToken)
    {
        // Custom validation logic
        return !await IsBlacklisted(from);
    }
    
    public async Task<bool> CanDeliverToAsync(ISmtpSession session, string to, string from, CancellationToken cancellationToken)
    {
        // Check if recipient exists
        return await UserExists(to);
    }
}

var server = new SmtpServerBuilder()
    .MailboxFilter(new CustomMailboxFilter())
    .Build();

// Combine multiple filters with AND logic
using Zetian.Enums;
using Zetian.Server;
using Zetian.Storage;

var compositeFilter = new CompositeMailboxFilter(CompositeMode.All)
    .AddFilter(new DomainMailboxFilter().AllowFromDomains("trusted.com"))
    .AddFilter(new CustomSpamFilter())
    .AddFilter(new RateLimitFilter());

var server = new SmtpServerBuilder()
    .MailboxFilter(compositeFilter)
    .Build();

server.MessageReceived += async (sender, e) =>
{
    var message = e.Message;
    
    // Access message details
    Console.WriteLine($"From: {message.From?.Address}");
    Console.WriteLine($"To: {string.Join(", ", message.Recipients)}");
    Console.WriteLine($"Subject: {message.Subject}");
    Console.WriteLine($"Size: {message.Size} bytes");
    
    // Get message content
    var textBody = message.TextBody;
    var htmlBody = message.HtmlBody;
    
    // Save to file
    await message.SaveToFileAsync($"{message.Id}.eml");
    
    // Reject if needed
    if (IsSpam(message))
    {
        e.Cancel = true;
        e.Response = new SmtpResponse(550, "Rejected as spam");
    }
};

server.AddRateLimiting(RateLimitConfiguration.PerHour(100));

server.AddSpamFilter(new[] { "spam.com", "junk.org" });
server.AddSizeFilter(10 * 1024 * 1024); // 10MB max

server.AddAllowedDomains("example.com", "mycompany.com");

server.SaveMessagesToDirectory(@"C:\smtp_messages");

using Zetian.Server;

var server = new SmtpServerBuilder()
    .WithFileMessageStore(@"C:\mail")  // Saves at protocol level
    .WithSenderDomainWhitelist("trusted.com")  // Rejects at MAIL FROM
    .WithRecipientDomainWhitelist("mydomain.com")  // Rejects at RCPT TO
    .Build();