SMTP Server basic functionality

MailServer/MailServer/Configuration.cs

@@ -0,0 +1,12 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace MailServer
+{
+    public class Configuration
+    {
+        public const string Hostname = "localhost";
+        public bool STARTTLS_Active = false;
+    }
+}

MailServer/MailServer/Database.cs

@@ -1,6 +1,7 @@
 using Microsoft.EntityFrameworkCore;
 using System;
 using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
 using System.IO;
 using System.Linq;
 using System.Text;
@@ -18,6 +19,12 @@ namespace SMTPServer
 
         public DbSet<Accounts> Accounts { get; set; }
 
+        public DbSet<Folders> Folders { get; set; }
+
+        public DbSet<Aliases> Aliases { get; set; }
+
+        public DbSet<Mails> Mails { get; set; }
+
         protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
             => optionsBuilder.UseMySql(@"Server=" + Hostname + ";database=" + DatabaseName + ";uid=" + Uid + ";pwd=" + Pwd + ";");
     }
@@ -32,9 +39,55 @@ namespace SMTPServer
     public class Accounts
     {
         public int Id { get; set; }
+        [MaxLength(255)]
         public string Name { get; set; }
         public int Domain { get; set; }
         public string Password { get; set; }
+        public bool CatchAll { get; set; }
         public bool Active { get; set; }
     }
+
+    public class Folders
+    {
+        public int Id { get; set; }
+        public int AccountId { get; set; }
+        [MaxLength(100)]
+        public string Name { get; set; }
+        public int StandardFolder { get; set; }
+    }
+
+    public enum StandardFolders
+    {
+        INBOX = 1,
+        TRASH = 2,
+        SPAM = 3
+    }
+
+    public class Aliases
+    {
+        public int Id { get; set; }
+        [MaxLength(255)]
+        public string SourceName { get; set; }
+        public int SourceDomain { get; set; }
+        public int DestinationAccount { get; set; }
+    }
+
+    public class Mails
+    {
+        public int Id { get; set; }
+        public int AccountId { get; set; }
+        public DateTime ReceiveDate { get; set; }
+        public string Data { get; set; }
+        
+        [MaxLength(15)]
+        public string SendedByServerIp { get; set; }
+
+        [MaxLength(255)]
+        public string From { get; set; }
+
+        [MaxLength(255)]
+        public string To { get; set; }
+        public int Folder { get; set; }
+        public bool Readed { get; set; }
+    }
 }

MailServer/MailServer/DatabaseHelper.cs

@@ -0,0 +1,52 @@
+using MailServer.Exceptions;
+using SMTPServer;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace MailServer
+{
+    class DatabaseHelper
+    {
+        MysqlDB DBContext;
+        public DatabaseHelper()
+        {
+            DBContext = new MysqlDB();
+            DBContext.Database.EnsureCreatedAsync();
+        }
+
+        public Folders GetInboxFromAccount(int accountid) => GetStandardFolderFromAccount(accountid, StandardFolders.INBOX);
+
+        public Folders GetStandardFolderFromAccount(int accountid, StandardFolders folder)
+        {
+            var res = DBContext.Folders.Where(x => x.AccountId.Equals(accountid) && x.StandardFolder.Equals(folder));
+            if (res.Count() < 1) throw new NotFoundException("Folder for specified account not found", Exceptions.Type.FOLDER);
+            return res.FirstOrDefault();
+        }
+
+        public Accounts GetAccount(string name, string domain) => GetAccount(name, GetDomain(domain).Id);
+
+        public Accounts GetAccount(string name, int domain)
+        {
+            name = name.ToLower();
+            var res = DBContext.Accounts.Where(x => x.Domain.Equals(domain) && x.Name.Equals(name));
+            if (res.Count() < 1) throw new NotFoundException("no account found", Exceptions.Type.ACCOUNT);
+            return res.FirstOrDefault();
+        }
+
+        public Domains GetDomain(string domain)
+        {
+            domain = domain.ToLower();
+            var res = DBContext.Domains.Where(x => x.Domain.Equals(domain));
+            if (res.Count() < 1) throw new NotFoundException("no domain found", Exceptions.Type.DOMAIN);
+            return res.FirstOrDefault();
+        }
+
+        public void AddMail(Mails mail)
+        {
+            DBContext.Add(mail);
+            DBContext.SaveChangesAsync();
+        }
+    }
+}

MailServer/MailServer/Exceptions/NotFoundException.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace MailServer.Exceptions
+{
+    class NotFoundException : Exception
+    {
+        public Type Type { get; set; }
+
+        public NotFoundException(Type type) : base()
+        {
+            Type = type;
+        }
+
+        public NotFoundException(string message, Type type) : base(message)
+        {
+            Type = type;
+        }
+
+        public NotFoundException(string message, Exception inner, Type type) : base(message, inner)
+        {
+            Type = type;
+        }
+    }
+
+    public enum Type
+    {
+        DOMAIN,
+        ACCOUNT,
+        ALIAS,
+        MAIL,
+        FOLDER
+    }
+}

MailServer/MailServer/GlobalSuppressions.cs

@@ -1,20 +0,0 @@
-
-// This file is used by Code Analysis to maintain SuppressMessage 
-// attributes that are applied to this project.
-// Project-level suppressions either have no target or are given 
-// a specific target and scoped to a namespace, type, member, etc.
-
-[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("Stil", "IDE1006:Benennungsstile", Justification = "<Ausstehend>", Scope = "member", Target = "~P:SMTPServer.MailQueue.QueueMail._Count")]
-[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("Stil", "IDE1006:Benennungsstile", Justification = "<Ausstehend>", Scope = "member", Target = "~P:SMTPServer.MailQueue.QueueMail._Mail")]
-[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("Stil", "IDE1006:Benennungsstile", Justification = "<Ausstehend>", Scope = "member", Target = "~P:SMTPServer.MailQueue.QueueMail._QueueEntered")]
-[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("Stil", "IDE1006:Benennungsstile", Justification = "<Ausstehend>", Scope = "member", Target = "~P:SMTPServer.MailQueue.QueueMail._DestinationIps")]
-[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("Stil", "IDE1006:Benennungsstile", Justification = "<Ausstehend>", Scope = "member", Target = "~P:SMTPServer.MailQueue.QueueMail._DestinationDnsNames")]
-[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("Stil", "IDE1006:Benennungsstile", Justification = "<Ausstehend>", Scope = "member", Target = "~P:SMTPServer.Mail._From")]
-[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("Stil", "IDE1006:Benennungsstile", Justification = "<Ausstehend>", Scope = "member", Target = "~P:SMTPServer.Mail._To")]
-[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("Stil", "IDE1006:Benennungsstile", Justification = "<Ausstehend>", Scope = "member", Target = "~P:SMTPServer.Mail._Subject")]
-[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("Stil", "IDE1006:Benennungsstile", Justification = "<Ausstehend>", Scope = "member", Target = "~P:SMTPServer.Mail._Others")]
-[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("Stil", "IDE1006:Benennungsstile", Justification = "<Ausstehend>", Scope = "member", Target = "~P:SMTPServer.Mail._Date")]
-[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("Stil", "IDE1006:Benennungsstile", Justification = "<Ausstehend>", Scope = "member", Target = "~P:SMTPServer.Mail._MessageId")]
-[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("Stil", "IDE1006:Benennungsstile", Justification = "<Ausstehend>", Scope = "member", Target = "~P:SMTPServer.Mail._MIME_Version")]
-[assembly: System.Diagnostics.CodeAnalysis.SuppressMessage("Stil", "IDE1006:Benennungsstile", Justification = "<Ausstehend>", Scope = "member", Target = "~P:SMTPServer.MailQueue.QueueMail._DestinationIndex")]
-

MailServer/MailServer/MTASession.cs

@@ -1,86 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-using System.Threading;
-
-namespace SMTPServer
-{
-    class MTASession
-    {
-        private static MTACommandsDict MTACommandsDict = new MTACommandsDict();
-        private ConnectedEventArgs ConnectedEventArgs { get; set; }
-
-        private bool Initialized { get; set; }
-        private string SenderHostname { get; set; }
-
-        private bool AuthActive { get; set; }
-        private string Username { get; set; }
-        private string Password { get; set; }
-        private bool Authenticated { get; set; }
-
-        private bool DATA { get; set; }
-
-        private string Mail_From { get; set; }
-
-        public MTASession(ConnectedEventArgs e)
-        {
-            ConnectedEventArgs = e;
-            Thread th = new Thread(new ThreadStart(StartCommunication));
-            th.Start();
-        }
-
-        private void StartCommunication()
-        {
-            ConnectedEventArgs.SendResponse(ResponseCodes.C220, MailTransferAgent.Hostname);
-            ConnectedEventArgs.NewLine += ConnectedEventArgs_NewLine;
-        }
-
-        private void ConnectedEventArgs_NewLine(string line)
-        {
-            if (line.StartsWith(MTACommandsDict[MTACommands.RSET]))
-            {
-                // Schauen was alles resettet wird
-            }
-
-            if (!Initialized)
-            {
-                if (line.StartsWith(MTACommandsDict[MTACommands.HELO]))
-                {
-                    ConnectedEventArgs.SendResponse(ResponseCodes.C250, MailTransferAgent.Hostname);
-                    //} else if (line.StartsWith(MTACommandsDict[MTACommands.EHLO])) {
-                    //    ConnectedEventArgs.SendResponse(ResponseCodes.C250, MailTransferAgent.Hostname);
-                }
-                else
-                {
-                    ConnectedEventArgs.SendResponse(ResponseCodes.C503, MailTransferAgent.Hostname);
-                    return;
-                }
-                Initialized = true;
-            }
-
-            if (line.StartsWith(MTACommandsDict[MTACommands.AUTH_LOGIN]))
-            {
-                AuthActive = true;
-                ConnectedEventArgs.SendResponse(ResponseCodes.C334);
-            }
-            else if (line.StartsWith(MTACommandsDict[MTACommands.MAIL_FROM]))
-            {
-                var args = line.Split(':');
-                if (args.Length < 2)
-                {
-                    ConnectedEventArgs.SendResponse(ResponseCodes.C501);
-                    return;
-                }
-                var mailFrom = args[1];
-                mailFrom.Replace('<', ' ');
-            }
-            else if (line.StartsWith(MTACommandsDict[MTACommands.QUIT]))
-            {
-                //throw new NotImplementedException();
-            } else
-            {
-                ConnectedEventArgs.SendResponse(ResponseCodes.C500);
-            }
-        }
-    }
-}

MailServer/MailServer/Mail.cs

@@ -2,25 +2,20 @@
 using System.Collections.Generic;
 using System.Text;
 
-namespace SMTPServer
+namespace MailServer
 {
     public class Mail
     {
-        public string To { get; private set; }
         public string From { get; private set; }
+        public string To { get; private set; }
 
-        public string Subject { get; private set; }
+        public string Data { get; set; }
-        public string MessageId { get; private set; }
-        public string Date { get; private set; }
 
-        public string MIME_Version { get; private set; }
+        public Mail(string from, string to, string data)
-
-        public string Others { get; private set; }
-
-
-        public Mail(string mail)
         {
-
+            From = from;
+            To = to;
+            Data = data;
         }
 
         public string GetSenderDomain()

MailServer/MailServer/MailQueue.cs

@@ -1,9 +1,11 @@
 using DnsClient;
+using MailServer;
+using SMTPServer;
 using SMTPServer.Exceptions;
 using System;
 using System.Collections.Generic;
 
-namespace SMTPServer
+namespace MailServer
 {
     public class MailQueue
     {
@@ -11,8 +13,9 @@ namespace SMTPServer
 
         public static async void AddToMesssageQueueAsync(Mail mail)
         {
+#pragma warning disable IDE0017 // Die Objektinitialisierung kann vereinfacht werden.
             var qmail = new QueueMail(mail);
-
+#pragma warning restore IDE0017 // Die Objektinitialisierung kann vereinfacht werden.
             qmail.DestinationDnsNames = await GetDNSEntries.GetMXRecordAsync(mail.GetSenderDomain());
             qmail.DestinationIps = await GetDNSEntries.GetIPAddressFromDnsArrayAsync(qmail.DestinationDnsNames);
 

MailServer/MailServer/MailServer.csproj

@@ -1,4 +1,4 @@
-<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" />
   <PropertyGroup Label="Configuration">
     <NoWarn>1701;1702;1705;1006</NoWarn>
@@ -18,13 +18,12 @@
     <EmbeddedResource Remove="DNSClient\**" />
     <EmbeddedResource Remove="DNS\**" />
   </ItemGroup>
-  <ItemGroup />
   <ItemGroup>
     <PackageReference Include="DnsClient">
       <Version>1.0.0-beta-1011</Version>
     </PackageReference>
     <PackageReference Include="Microsoft.DotNet.Cli.Utils">
-      <Version>1.0.0-preview2-1-003177</Version>
+      <Version>1.0.0-preview3-004056</Version>
     </PackageReference>
     <PackageReference Include="Microsoft.EntityFrameworkCore.Tools">
       <Version>1.1.0-preview4-final</Version>
@@ -58,7 +57,7 @@
       <Version>1.1.0-rtm-10012</Version>
     </PackageReference>
     <PackageReference Include="System.IO.FileSystem">
-      <Version>4.0.1</Version>
+      <Version>4.3.0</Version>
     </PackageReference>
     <PackageReference Include="System.Net.NameResolution">
       <Version>4.3.0</Version>

MailServer/MailServer/MailTransferAgent.cs

@@ -4,12 +4,13 @@ using System.Text;
 using System.Threading;
 using SMTPServer.Exceptions;
 using System.Net;
+using MailServer.SMTPServer;
 
 namespace SMTPServer
 {
     class MailTransferAgent
     {
-        public const string Hostname = "mail.fstamm.net";
+       /* public const string Hostname = "mail.fstamm.net";
         private static MTACommandsDict MTACommandsDict = new MTACommandsDict();
         private static Thread Thread;
         private static List<MTASession> Sessions { get; set; }
@@ -62,6 +63,6 @@ namespace SMTPServer
         {
 
             return null;
-        }
+        }*/
     }
 }

MailServer/MailServer/PortListener.cs

@@ -1,4 +1,5 @@
-using SMTPServer.Exceptions;
+using MailServer.SMTPServer;
+using SMTPServer.Exceptions;
 using System;
 using System.Collections.Generic;
 using System.Net;
@@ -12,9 +13,7 @@ namespace SMTPServer
 
     public class ConnectedEventArgs : EventArgs
     {
-        public delegate void ReceivedLineEventHandler(string line);
+        
-
-        public event ReceivedLineEventHandler NewLine;
 
         private Encoding Encoding { get; set; }
         private string Others { get; set; }
@@ -71,7 +70,7 @@ namespace SMTPServer
                     if (c.Equals('\n'))
                     {
                         Console.WriteLine(line);
-                        NewLine(line);
+                        //NewLine(line);
                         line = "";
                     }
                     else line += c;

MailServer/MailServer/Program.cs

@@ -35,8 +35,10 @@ namespace SMTPServer
             //t.Start();
             //TestAsync();
 
-            var listener = new PortListener(5122);
+            //var listener = new PortListener(5122);
-            listener.OnConnected += Listener_OnConnected;
+            //listener.OnConnected += Listener_OnConnected;
+
+            var l = new MailServer.SMTPServer.SmtpPortListener(5122);
 
             while (true)
             {
@@ -60,7 +62,7 @@ namespace SMTPServer
 
         private static void Listener_OnConnected(object source, ConnectedEventArgs e)
         {
-            var session = new MTASession(e);
+            //var session = new MTASession(e);
             //throw new NotImplementedException();
         }
         /*

MailServer/MailServer/SMTPServer/MTACommands.cs

@@ -4,7 +4,7 @@ using System.IO;
 using System.Linq;
 using System.Text;
 
-namespace SMTPServer
+namespace MailServer.SMTPServer
 {
     public class MTACommandsDict : Dictionary<MTACommands, String>
     {

MailServer/MailServer/SMTPServer/SmtpCommand.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace MailServer.SMTPServer
+{
+    public class SmtpCommand
+    {
+        public string Command { get; set; }
+        public string[] Parameters { get; set; }
+
+        public SmtpCommand(string command)
+        {
+            Parameters = new string[0];
+            if (command.Length == 0)
+            {
+                Command = "FREELINE";
+                return;
+            }
+            else if (command.Equals("."))
+            {
+                Command = "JUSTADOT";
+                return;
+            }
+# if DEBUG
+            else if (command.Equals("<CRLF>.<CRLF>"))
+            {
+                Command = "DATAEND";
+                return;
+            }
+# endif
+
+            var sp = command.Split(' ');
+
+            Command = sp[0];
+
+            if (sp.Length < 2) return;
+            Parameters = new string[sp.Length - 1];
+            for (int i = 1; i < sp.Length; i++)
+            {
+                Parameters[i - 1] = sp[i];
+            }
+        }
+    }
+}

MailServer/MailServer/SMTPServer/SmtpPortListener.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+using System.Net;
+using System.Net.Sockets;
+using System.Text;
+using System.Threading;
+
+namespace MailServer.SMTPServer
+{
+    public class SmtpPortListener
+    {
+        private static List<int> Ports { get; set; }
+        private int Port { get; set; }
+        private TcpListener Listener;
+        private List<SmtpServerSession> Sessions { get; set; }
+
+        public SmtpPortListener(int port)
+        {
+            Sessions = new List<SmtpServerSession>();
+            Port = port;
+            Thread thread = new Thread(StartListeningAsync);
+            thread.Start();
+        }
+
+        public async void StartListeningAsync()
+        {
+            Listener = new TcpListener(IPAddress.Any, Port);
+            Listener.Start();
+
+            while (true)
+            {
+                //var socket = await Listener.AcceptSocketAsync();
+                var client = await Listener.AcceptTcpClientAsync();
+                var session = new SmtpServerSession(client);
+                Sessions.Add(session);
+            }
+        }
+    }
+}

MailServer/MailServer/SMTPServer/SmtpServerSession.cs

@@ -0,0 +1,297 @@
+using SMTPServer;
+using System;
+using System.Collections.Generic;
+using System.Net.Sockets;
+using System.Text;
+using System.Linq;
+
+namespace MailServer.SMTPServer
+{
+    class SmtpServerSession : SmtpSession
+    {
+        private bool Initialized { get; set; }
+        private string SenderHostname { get; set; }
+
+        private bool MailFromSet { get; set; }
+        private string MailFrom { get; set; }
+
+        private List<string> Recipients { get; set; }
+
+        private bool WaitForData { get; set; }
+        private string Data { get; set; }
+        private bool FreeLine { get; set; }
+
+        private bool AuthActive { get; set; }
+        private string Username { get; set; }
+        private string Password { get; set; }
+        private bool Authenticated { get; set; }
+
+        public SmtpServerSession(TcpClient client) : base(client) {
+            Recipients = new List<string>();
+            SendResponse(ResponseCodes.C220, Configuration.Hostname + " Welcome to SimpleMail DotNetCore based AIO MailServer");
+            NewLine += SmtpServerSession_NewLine;
+        }
+
+        private void SmtpServerSession_NewLine(string line)
+        {
+            try
+            {
+                var command = new SmtpCommand(line);
+
+                if (WaitForData)
+                {
+#if DEBUG
+                    bool dataend = false;
+                    if (command.Command.Equals("DATAEND"))
+                    {
+                        dataend = true;
+                    }
+#endif
+                    if (!FreeLine && command.Command.Equals("FREELINE"))
+                    {
+                        FreeLine = true;
+                        return;
+                    }
+                    else if ((FreeLine && command.Command.Equals("JUSTADOT")) || dataend)
+                    {
+                        SendResponse(ResponseCodes.C250, "OK");
+                        foreach (var r in Recipients)
+                        {
+                            var split = r.Split('@');
+                            var name = split[0];
+                            var domain = split[1];
+
+                            using (var context = new MysqlDB())
+                            {
+                                context.Database.EnsureCreated();
+                                int accountId = 0;
+
+                                var dmn = context.Domains.Where(x => x.Domain.Equals(domain));
+                                var domainidx = dmn.FirstOrDefault().Id;
+
+                                var res = context.Accounts.Where(x => x.Domain.Equals(domainidx) && x.Name.Equals(name));
+                                if (res.Count() < 1)
+                                {
+                                    var res2 = context.Aliases.Where(x => x.SourceName.Equals(name) && x.SourceDomain.Equals(domain));
+                                    if (res2.Count() < 1)
+                                    {
+                                        var res3 = context.Accounts.Where(x => x.Domain.Equals(domain) && x.CatchAll == true);
+                                        if (res3.Count() < 1)
+                                        {
+                                            //ToDo unmöglich machen!!
+                                        }
+                                        else
+                                        {
+                                            accountId = res3.FirstOrDefault().Id;
+                                        }
+                                    }
+                                    else
+                                    {
+                                        accountId = res2.FirstOrDefault().DestinationAccount;
+                                    }
+                                }
+                                else
+                                {
+                                    accountId = res.FirstOrDefault().Id;
+                                }
+                                int folderid = 0;
+
+                                var res4 = context.Folders.Where(x => x.AccountId == accountId && x.StandardFolder == (int)StandardFolders.INBOX);
+                                if (res4.Count() < 1)
+                                {
+                                    //ToDo ERROR
+                                    folderid = 0;
+                                }
+                                else folderid = res4.FirstOrDefault().Id;
+
+                                var nm = new Mails()
+                                {
+                                    AccountId = accountId,
+                                    ReceiveDate = DateTime.Now,
+                                    Data = Data,
+                                    SendedByServerIp = "0.0.0.0",
+                                    From = MailFrom,
+                                    To = r,
+                                    Folder = folderid
+                                };
+
+                                context.Mails.Add(nm);
+                                context.SaveChangesAsync();
+                            }
+
+                            return;
+                        }
+                        SendResponse(ResponseCodes.C250, "OK");
+                        return;
+                    }
+                    else
+                    {
+                        Data += command.Command;
+
+                        foreach (var s in command.Parameters)
+                        {
+                            Data += " " + s;
+                        }
+
+                        Data += "\n";
+                        FreeLine = false;
+                    }
+                    return;
+                }
+
+                switch (command.Command.ToUpper())
+                {
+                    case "HELO":
+                        if (command.Parameters.Length < 1)
+                        {
+                            SendResponse(ResponseCodes.C501, "Hostname Required");
+                            return;
+                        }
+                        SenderHostname = command.Parameters[0];
+                        Initialized = true;
+                        SendResponse(ResponseCodes.C250, "OK");
+                        return;
+                    case "RSET":
+                        //ToDo 
+                        return;
+                    case "QUIT":
+                        SendResponse(ResponseCodes.C221, Configuration.Hostname + " closing transmission channel");
+                        CloseAll();
+                        return;
+                }
+
+                if (Initialized)
+                {
+                    switch (command.Command.ToUpper())
+                    {
+                        case "MAIL":
+                            if (command.Parameters.Length < 1)
+                            {
+                                SendResponse(ResponseCodes.C501);
+                                return;
+                            }
+                            if (!command.Parameters[0].ToUpper().StartsWith("FROM"))
+                            {
+                                SendResponse(ResponseCodes.C501);
+                                return;
+                            }
+                            if (command.Parameters.Length == 1)
+                            {
+                                var m = command.Parameters[0].Split(':');
+                                if (m.Length != 2)
+                                {
+                                    SendResponse(ResponseCodes.C501);
+                                    return;
+                                }
+                                MailFrom = m[1];
+                            }
+                            else if (command.Parameters.Length == 2)
+                            {
+                                MailFrom = command.Parameters[1];
+                            }
+                            else
+                            {
+                                SendResponse(ResponseCodes.C501);
+                                return;
+                            }
+
+                            MailFrom.Replace("<", String.Empty);
+                            MailFrom.Replace(">", String.Empty);
+                            MailFromSet = true;
+                            SendResponse(ResponseCodes.C250, "OK");
+                            return;
+                    }
+
+                    if (MailFromSet)
+                    {
+                        switch (command.Command.ToUpper())
+                        {
+                            case "RCPT":
+                                if (command.Parameters.Length < 1)
+                                {
+                                    SendResponse(ResponseCodes.C501);
+                                    return;
+                                }
+                                if (!command.Parameters[0].ToUpper().StartsWith("TO"))
+                                {
+                                    SendResponse(ResponseCodes.C501);
+                                    return;
+                                }
+
+                                var rcpt = "";
+                                if (command.Parameters.Length == 1)
+                                {
+                                    var m = command.Parameters[0].Split(':');
+                                    if (m.Length != 2)
+                                    {
+                                        SendResponse(ResponseCodes.C501);
+                                        return;
+                                    }
+                                    rcpt = m[1];
+                                }
+                                else if (command.Parameters.Length == 2)
+                                {
+                                    rcpt = command.Parameters[1];
+                                }
+                                else
+                                {
+                                    SendResponse(ResponseCodes.C501);
+                                    return;
+                                }
+
+                                rcpt = rcpt.Replace("<", String.Empty);
+                                rcpt = rcpt.Replace(">", String.Empty);
+
+                                var split = rcpt.Split('@');
+                                if (split.Length != 2)
+                                {
+                                    SendResponse(ResponseCodes.C501);
+                                    return;
+                                }
+
+                                using (var context = new MysqlDB())
+                                {
+                                    context.Database.EnsureCreated();
+                                    var res = context.Domains.Where(x => x.Domain.Equals(split[1]));
+                                    if (res.Count() < 1)
+                                    {
+                                        SendResponse(ResponseCodes.C550, "No such user here");
+                                        return;
+                                    }
+                                }
+
+                                Recipients.Add(rcpt);
+                                SendResponse(ResponseCodes.C250, "OK");
+                                return;
+                        }
+
+                        if (Recipients.Count > 0)
+                        {
+                            switch (command.Command.ToUpper())
+                            {
+                                case "DATA":
+                                    SendResponse(ResponseCodes.C354, "Start mail input, end with <CRLF>.<CRLS>");
+                                    WaitForData = true;
+                                    return;
+                            }
+                        }
+                    }
+                    SendResponse(ResponseCodes.C500, command.Command);
+                    //throw new NotImplementedException();
+                }
+            } catch (Exception e)
+            {
+                Logging.AddException(e);
+                SendResponse(ResponseCodes.C554, "internal error");
+                SendResponse(ResponseCodes.C221, "Closing Transmission");
+                CloseAll();
+            }
+        }
+        
+        private void ClearFields()
+        {
+            //ToDo einbauen
+        }
+
+    }
+}

MailServer/MailServer/SMTPServer/SmtpSession.cs

@@ -0,0 +1,103 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Net.Sockets;
+using System.Text;
+using System.Threading;
+
+namespace MailServer.SMTPServer
+{
+    public delegate void ReceivedLineEventHandler(string line);
+
+    class SmtpSession
+    {
+        public event ReceivedLineEventHandler NewLine;
+
+        private TcpClient Client { get; set; }
+        private NetworkStream Stream { get; set; }
+        private Encoding Encoding = Encoding.ASCII;
+        private string Others;
+        private Thread Worker;
+        private bool Active = true;
+
+        public SmtpSession(TcpClient client)
+        {
+            Client = client;
+            Stream = client.GetStream();
+            Others = "";
+            Worker = new Thread(ReadClientInput);
+            Worker.Start();
+        }
+
+        public void SendResponse(ResponseCodes responseCode) => SendResponse(responseCode, "");
+
+        public void SendResponse(ResponseCodes responseCode, string args)
+        {
+            var text = ((int)responseCode).ToString();
+            text += " " + args +'\r' + '\n';
+            var bytes = Encoding.UTF8.GetBytes(text);
+            Stream.Write(bytes, 0, bytes.Length);
+        }
+
+        private void ReadClientInput()
+        {
+            while (Active)
+            {
+                if (Stream.DataAvailable)
+                {
+                    byte[] buffer = new byte[Client.ReceiveBufferSize];
+                    var readed = Stream.Read(buffer, 0, buffer.Length);
+
+                    var str = Encoding.GetString(buffer, 0, readed);
+                    lock (Others)
+                    {
+                        Others += str;
+                    }
+
+                    CheckLines();
+                }
+                else
+                {
+                    Thread.Sleep(10);
+                }
+            }
+        }
+
+        private bool r = false;
+
+        private void CheckLines()
+        {
+            lock (Others)
+            {
+                var line = "";
+                foreach (char c in Others)
+                {
+                    if (c.Equals('\r'))
+                    {
+                        r = true;
+                    }
+                    else if (r && c.Equals('\n'))
+                    {
+                        //Console.WriteLine(line);
+                        NewLine(line);
+                        line = "";
+                    }
+                    else
+                    {
+                        line += c;
+                        r = false;
+                    }
+                }
+                Others = line;
+            }
+        }
+
+        public void CloseAll()
+        {
+            Stream.Dispose();
+            Client.Dispose();
+            Active = false;
+        }
+    }
+}