Utmaning i programmering

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;
using System.Net.Mail;
using System.IO;
using System.Net;

namespace ConsoleApplication1
{
    class Program
    {
        static List<string> Addresses = new List<string>(); static NetworkCredential cred;
        static string menu = "\n\nMeny\n\n - Adresser hittades: {0}\n\n1.Skriv ett meddelande till allihopa\t2.Skriv separat meddelande till samtliga\n3.Byt konto att skicka från\nVal: ";

        static void Main(string[] args)
        {
            cred = User();
            Console.Write("Registrerat från-adress\n\nSkriv in adressen till filen: ");
            string input = Console.ReadLine();

            Addresses = Mail.ToList(@input);
            
            PrintMenu();


            switch (Console.ReadKey().Key)
            {
                case ConsoleKey.D1:
                    ToAllSend();
                    break;
                case ConsoleKey.NumPad1: goto case ConsoleKey.D1;
                case ConsoleKey.D2:
                    PerAddressSend();
                    break;
                case ConsoleKey.NumPad2: goto case ConsoleKey.D2;
                case ConsoleKey.D3:
                    User();
                    break;
                case ConsoleKey.NumPad3: goto case ConsoleKey.D3;
                default:
                    Console.Clear();
                    PrintMenu();
                    break;
            }


            Console.ReadKey();
        }

        /// <summary>
        /// Prints the default menu
        /// </summary>
        public static void PrintMenu()
        {
            Console.Write(menu, Addresses.Count);
        }

        /// <summary>
        /// Sends a message to every address found.
        /// </summary>
        private static void ToAllSend()
        {
            Console.Write("Ämne: ");
            Mail.Subject = Console.ReadLine();

            Console.Write("Innehåll: ");
            Mail.Body = Console.ReadLine();


            for (int i = 0; i < Addresses.Count; i++)
            {
                if (Addresses[i].Length > 5)
                {
                    Client.Send(cred, Addresses[i], Mail.Subject, Mail.Body);
                }
            }
            Console.WriteLine("Alla jobb klara.");
        }

        /// <summary>
        /// Sends message to each and every address individually
        /// </summary>
        private static void PerAddressSend()
        {
            for (int i = 0; i < Addresses.Count; i++)
            {
                Console.Write("\n\nÄmne: ");
                Mail.Subject = Console.ReadLine();

                Console.Write("\nInnehåll: ");
                Mail.Body = Console.ReadLine();

                if (Addresses[i].Length > 5)
                {
                    Client.Send(cred, Addresses[i], Mail.Subject, Mail.Body);
                }
                Console.WriteLine("Jobb utfört.");
            }
            Console.WriteLine("\n\nAlla jobb klara.");
        }

        /// <summary>
        /// Initializes new credentials for a user to send from
        /// </summary>
        private static NetworkCredential User()
        {
            Console.Clear();
            Console.Write("Vilken e-post vill du skicka från?\n\nDin e-post: ");
            string sendEmailsFrom = Console.ReadLine();
            Console.Write("\nLösenord: ");
            Console.ForegroundColor = ConsoleColor.Black;
            string sendEmailsFromPassword = Console.ReadLine();
            Console.ForegroundColor = ConsoleColor.Gray;
            NetworkCredential cred = new NetworkCredential(sendEmailsFrom, sendEmailsFromPassword);
            Console.Clear();
            return cred;
        }
    }

    public class Client
    {
        public static void Send(NetworkCredential cred, string to, string subject, string body)
        {
            MailMessage mailMessage = new MailMessage();
            mailMessage.To.Add(to);
            mailMessage.Subject = subject;
            mailMessage.Body = body;
            mailMessage.IsBodyHtml = true;
            mailMessage.From = new MailAddress(cred.UserName);

            SmtpClient mailClient = new SmtpClient("smtp.gmail.com", 587);
            mailClient.EnableSsl = true;
            mailClient.DeliveryMethod = SmtpDeliveryMethod.Network;
            mailClient.UseDefaultCredentials = false;
            mailClient.Timeout = 8000;
            mailClient.Credentials = cred;
            mailClient.Send(mailMessage);
        }
    }

    class Mail
    {
        /// <summary>
        /// Containing text
        /// </summary>
        public static string Body { get; set; }

        /// <summary>
        /// What subject the mail has
        /// </summary>
        public static string Subject { get; set; }

        /// <summary>
        /// Which mailaddress to send to
        /// </summary>
        public static string To { get; set; }

        /// <summary>
        /// The stored address to the file
        /// </summary>
        private static string p_CurrentFileAdress;

        /// <summary>
        /// Returns a list of string with the content found in the file
        /// </summary>
        /// <param name="directory">Directory of which file to read from</param>
        /// <returns>List of addresses</returns>
        public static List<string> ToList(string directory)
        {
            List<string> tempList = new List<string>();
            if (LoadFile(directory))
            {
                using (StreamReader sr = new StreamReader(p_CurrentFileAdress, Encoding.UTF8))
                {
                    string p_AtLine = "";
                    while ((p_AtLine = sr.ReadLine()) != null)
                    {
                        try
                        {
                            if (p_AtLine.Length > 5)
                            {
                                if (p_AtLine.Contains('@'))
                                {
                                    tempList.Add(p_AtLine);
                                }
                            }
                        }
                        catch (Exception)
                        {
                            Console.WriteLine("Inte en giltig adress.");
                        }
                    }
                }
                return tempList;
            }
            else
            {
                return null;
            }
        }

        /// <summary>
        /// Determines wether the file is existing
        /// </summary>
        /// <param name="directory">The directory in which the file is located on the harddrive.</param>
        /// <returns>State wether the file is existing</returns>
        public static bool LoadFile(string directory)
        {
            if (File.Exists(directory))
            {
                p_CurrentFileAdress = directory;
                return true;
            }
            else
            {
                return false;
            }
        }

        public override string ToString()
        {
            return string.Format("Till: {0}\nÄmne: {1}\nInnehåll: {2}", To, Subject, Body);
        }
    }
    
}