dotnet-core_mail-server/MailServer/MailQueue.cs

using DnsClient;
using MailServer;
using SMTPServer;
using SMTPServer.Exceptions;
using System;
using System.Collections.Generic;

namespace MailServer
{
    public class MailQueue
    {
        private static List<QueueMail> Mails = null;

        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);

            lock (Mails)
            {
                if (Mails == null)
                {
                    Mails = new List<QueueMail>();
                }
                Mails.Add(qmail);
            }
        }

        public static QueueMail GetNextMail()
        {
            lock (Mails)
            {
                if(Mails.Count < 1)
                {
                    throw new NoMailsInQueueException();
                }
                
                var m = Mails[0];

                Mails.Remove(m);
                m.Count++;
                Mails.Add(m);

                return m;
            }
        }

        public static void RemoveMailFromQueue(QueueMail mail)
        {
            lock (Mails)
            {
                Mails.Remove(mail);
            }
        }

        public class QueueMail
        {
            public DateTime QueueEntered { get; private set; }
            public int Count { get; set; }
            public Mail Mail { get; private set; }
            public string[] DestinationIps { get; set; }
            public string[] DestinationDnsNames { get; set; }
            public int DestinationIndex { get; set; }

            public QueueMail (Mail mail)
            {
                Mail = mail;
                QueueEntered = DateTime.Now;
                Count = 0;
            }

            public byte[] GetIpBytes() => GetIpBytes(DestinationIndex);

            public byte[] GetIpBytes(int index)
            {
                var parts = DestinationIps[index].Split('.');
                var bytes = new byte[parts.Length];
                for(int i = 0; i < parts.Length; i++)
                {
                    bytes[i] = byte.Parse(parts[i]);
                }

                return bytes;
            }
        }
    }
}