This article Illustrate How to read mails from ASP.Net. Using POP commands you can access you email inbox from ASP.Net. Basic POP commands are USER, PASS, LIST, QUIT, RETR.
More details POP command help you can check these links

//Creating Object for POPHelper
//Parameters are Gmail,Yahoo or MSN Pop Server,
//Port number
//bool isSSL
POPHelper objPopHelper = new POPHelper("pop.gmail.com", 995, true);
objPopHelper.UserName = "Your Gmail Username eg:[email protected]";
objPopHelper.Password = "GmailPassword";
objPopHelper.Connect();
GridView1.DataSource = p.DataSource;
GridView1.DataBind();



Code Of Connect Method

public void Connect()
        {
            string response = string.Empty;
            ArrayList arrList = new ArrayList();
            try
            {
                //Connect to Host server
                #region Connect Host
                TcpClient _tcpClient = new TcpClient();
                try
                {
                    _tcpClient.Connect(_hostname, _port);
                    //if login is ssl
                    if (_isSsl)
                    {
                        _stream = new SslStream(_tcpClient.GetStream());
                        ((SslStream)_stream).AuthenticateAsClient(_hostname);
                    }
                    else
                    {
                        _stream = _tcpClient.GetStream();
                    }
                }
                catch (Exception ex)
                {
                    throw new POPCommandException("Connection to " + _hostname + " Port: " + _port + " failed. Error Details"+ex.Message);
                }
                #endregion
                // Send POP Commands (USER, PASS, LIST) to Host
                #region POP Commands
                _streamWriter = new StreamWriter(_stream, Encoding.ASCII);
                _streamReader = new StreamReader(_stream, Encoding.ASCII);

                //POP command for send Username
                _streamWriter.WriteLine(POPCommands.USER.ToString()+" "+ UserName);
                //send to server
                _streamWriter.Flush();

                //POP command for send  Password
                _streamWriter.WriteLine(POPCommands.PASS.ToString() + " " + Password);
                //send to server
                _streamWriter.Flush();

                //POP command for List mails
                _streamWriter.WriteLine(POPCommands.LIST.ToString());
                //send to server
                _streamWriter.Flush();
                #endregion
                //Read Response Stream from Host
                #region Read Response Srteam
                //Read Response Stream
                response = null;
                string resText = string.Empty;
                while ((resText = _streamReader.ReadLine()) != null)
                {
                    if (resText == ".")
                    { break; }
                    if (resText.IndexOf("-ERR") != -1)
                    { break; }
                    response += resText;
                    arrList.Add(resText);
                }
                #endregion
                //Binding Properties
                #region Bindings
                //Bind Message count
                BindMailCount(arrList);
                //mails returns List
                _mail = ReadMail(messagecount);
                //get  mails Subjects returns List
                _mailsub = FilterContent(_mail,FiltersOption.Subject);
                _from = FilterContent(_mail, FiltersOption.From);
                _to = FilterContent(_mail, FiltersOption.To);
                SetDataSource(_mailsub, _from);
                #endregion
            }
            catch (Exception ex)
            {
                errors.Add(ex.Message);
            }
        }

Class Diagram of POPHelper



Reading Mails Using POP Command RETR from ASP.NET

private List ReadMail(int Count)
        {
            List lst = new List();
            try
            {
                for (int i = 1; i <= Count; i++)
                {
                    _streamWriter.WriteLine(POPCommands.RETR+" " + i.ToString());
                    _streamWriter.Flush();
                    string resText = string.Empty;
                    while ((resText = _streamReader.ReadLine()) != null)
                    {
                        if (resText == ".")
                        { break; }
                        if (resText.IndexOf("-ERR") != -1)
                        { break; }
                        lst.Add(resText);
                    }
                }               

            }
            catch(Exception ex)
            {
                errors.Add(ex.Message);
            }
            return lst;
        }

Enumerates for Filer message subject and From Address and ToAddress



Method for Filer Content

private List FilterContent(List Mails,FiltersOption filter)
        {
            List filterItems = new List();
            try
            {
                for (int i = 0; i < Mails.Count; i++)
                {
                    if (Mails[i].StartsWith(filter.ToString() + ":"))
                    {
                        string sub = Mails[i].Replace(filter.ToString() + ":", "");
                        filterItems.Add(sub);
                    }
                }
            }
            catch (Exception ex)
            {
                errors.Add(ex.Message);
            }
            return filterItems;
        }

Creating DataSource for GridView

private DataTable SetDataSource(Listsubject,Listsender)
        {
            int messageCount = messagecount;
            dataTab = new DataTable();
            DataRow drow;
            DataColumn Sender = new DataColumn("Sender", typeof(string));
            DataColumn Subject = new DataColumn("Subject", typeof(string));
            dataTab.Columns.Add(Sender);
            dataTab.Columns.Add(Subject);
            for (int i = 0; i < subject.Count; i++)
            {
                drow = dataTab.NewRow();
                dataTab.Rows.Add(drow);
                dataTab.Rows[i][Sender] = sender[i].ToString();
                dataTab.Rows[i][Subject] = subject[i].ToString();
            }
            return dataTab;
        }

The above error message indicate that you haven’t configured your ASP.NET 4 on your IIS. To configure IIS7.0 to use ASP.NET 4, please follow this steps:

- Open command prompt under Administrative privileges.
- Navigate to this location C:\Windows\Microsoft.NET\Framework\v4.0.30319.
- Locate aspnet_regiis.exe file.
- Run the utility with –i switch to register ASP.NET 4.0 with IIS7



And you can see it will work now.