项目中在使用的POP3 接收邮件类库,亲测通过，附完整源码下载(OpenPOP.NET)

【实例截图】

【核心代码】

using System;
using System.Collections.Generic;
using System.Data;
using System.IO;
using System.Text;
using System.Windows.Forms;
using OpenPop.Mime;
using OpenPop.Mime.Header;
using OpenPop.Pop3;
using OpenPop.Pop3.Exceptions;
using OpenPop.Common.Logging;
using Message = OpenPop.Mime.Message;

namespace OpenPop.TestApplication
{
	/// <summary>
	/// This class is a form which makes it possible to download all messages
	/// from a pop3 mailbox in a simply way.
	/// </summary>
	public class TestForm : Form
	{
		private readonly Dictionary<int, Message> messages = new Dictionary<int, Message>();
		private readonly Pop3Client pop3Client;
		private Button connectAndRetrieveButton;
		private Button uidlButton;
		private Panel attachmentPanel;
		private ContextMenu contextMenuMessages;
		private DataGrid gridHeaders;
		private Label labelServerAddress;
		private Label labelServerPort;
		private Label labelAttachments;
		private Label labelMessageBody;
		private Label labelMessageNumber;
		private Label labelTotalMessages;
		private Label labelPassword;
		private Label labelUsername;
		private TreeView listAttachments;
		private TreeView listMessages;
		private MenuItem menuDeleteMessage;
		private MenuItem menuViewSource;
		private Panel panelTop;
		private Panel panelProperties;
		private Panel panelMiddle;
		private Panel panelMessageBody;
		private Panel panelMessagesView;
		private SaveFileDialog saveFile;
		private TextBox loginTextBox;
		private TextBox messageTextBox;
		private TextBox popServerTextBox;
		private TextBox passwordTextBox;
		private TextBox portTextBox;
		private TextBox totalMessagesTextBox;
		private ProgressBar progressBar;
		private CheckBox useSslCheckBox;

		private TestForm()
		{
			//
			// Required for Windows Form Designer support
			//
			InitializeComponent();

			//
			// User defined stuff here 
			//

			// This is how you would override the default logger type
			// Here we want to log to a file
			DefaultLogger.SetLog(new FileLogger());

			// Enable file logging and include verbose information
			FileLogger.Enabled = true;
			FileLogger.Verbose = true;

			pop3Client = new Pop3Client();

			// This is only for faster debugging purposes
			// We will try to load in default values for the hostname, port, ssl, username and password from a file
			string myDocs = Environment.GetFolderPath(Environment.SpecialFolder.Personal);
			string file = Path.Combine(myDocs, "OpenPopLogin.txt");
			if (File.Exists(file))
			{
				using (StreamReader reader = new StreamReader(File.OpenRead(file)))
				{
					// This describes how the OpenPOPLogin.txt file should look like
					popServerTextBox.Text = reader.ReadLine(); // Hostname
					portTextBox.Text = reader.ReadLine(); // Port
					useSslCheckBox.Checked = bool.Parse(reader.ReadLine() ?? "true"); // Whether to use SSL or not
					loginTextBox.Text = reader.ReadLine(); // Username
					passwordTextBox.Text = reader.ReadLine(); // Password
				}
			}
		}

		#region Windows Form Designer generated code
		/// <summary>
		///   Required method for Designer support - do not modify
		///   the contents of this method with the code editor.
		/// </summary>
		private void InitializeComponent()
		{
            System.ComponentModel.ComponentResourceManager resources = new System.ComponentModel.ComponentResourceManager(typeof(TestForm));
            this.panelTop = new System.Windows.Forms.Panel();
            this.useSslCheckBox = new System.Windows.Forms.CheckBox();
            this.uidlButton = new System.Windows.Forms.Button();
            this.totalMessagesTextBox = new System.Windows.Forms.TextBox();
            this.labelTotalMessages = new System.Windows.Forms.Label();
            this.labelPassword = new System.Windows.Forms.Label();
            this.passwordTextBox = new System.Windows.Forms.TextBox();
            this.labelUsername = new System.Windows.Forms.Label();
            this.loginTextBox = new System.Windows.Forms.TextBox();
            this.connectAndRetrieveButton = new System.Windows.Forms.Button();
            this.labelServerPort = new System.Windows.Forms.Label();
            this.portTextBox = new System.Windows.Forms.TextBox();
            this.labelServerAddress = new System.Windows.Forms.Label();
            this.popServerTextBox = new System.Windows.Forms.TextBox();
            this.panelProperties = new System.Windows.Forms.Panel();
            this.gridHeaders = new System.Windows.Forms.DataGrid();
            this.panelMiddle = new System.Windows.Forms.Panel();
            this.panelMessageBody = new System.Windows.Forms.Panel();
            this.progressBar = new System.Windows.Forms.ProgressBar();
            this.messageTextBox = new System.Windows.Forms.TextBox();
            this.labelMessageBody = new System.Windows.Forms.Label();
            this.panelMessagesView = new System.Windows.Forms.Panel();
            this.listMessages = new System.Windows.Forms.TreeView();
            this.contextMenuMessages = new System.Windows.Forms.ContextMenu();
            this.menuDeleteMessage = new System.Windows.Forms.MenuItem();
            this.menuViewSource = new System.Windows.Forms.MenuItem();
            this.labelMessageNumber = new System.Windows.Forms.Label();
            this.attachmentPanel = new System.Windows.Forms.Panel();
            this.listAttachments = new System.Windows.Forms.TreeView();
            this.labelAttachments = new System.Windows.Forms.Label();
            this.saveFile = new System.Windows.Forms.SaveFileDialog();
            this.panelTop.SuspendLayout();
            this.panelProperties.SuspendLayout();
            ((System.ComponentModel.ISupportInitialize)(this.gridHeaders)).BeginInit();
            this.panelMiddle.SuspendLayout();
            this.panelMessageBody.SuspendLayout();
            this.panelMessagesView.SuspendLayout();
            this.attachmentPanel.SuspendLayout();
            this.SuspendLayout();
            // 
            // panelTop
            // 
            this.panelTop.Controls.Add(this.useSslCheckBox);
            this.panelTop.Controls.Add(this.uidlButton);
            this.panelTop.Controls.Add(this.totalMessagesTextBox);
            this.panelTop.Controls.Add(this.labelTotalMessages);
            this.panelTop.Controls.Add(this.labelPassword);
            this.panelTop.Controls.Add(this.passwordTextBox);
            this.panelTop.Controls.Add(this.labelUsername);
            this.panelTop.Controls.Add(this.loginTextBox);
            this.panelTop.Controls.Add(this.connectAndRetrieveButton);
            this.panelTop.Controls.Add(this.labelServerPort);
            this.panelTop.Controls.Add(this.portTextBox);
            this.panelTop.Controls.Add(this.labelServerAddress);
            this.panelTop.Controls.Add(this.popServerTextBox);
            this.panelTop.Dock = System.Windows.Forms.DockStyle.Top;
            this.panelTop.Location = new System.Drawing.Point(0, 0);
            this.panelTop.Name = "panelTop";
            this.panelTop.Size = new System.Drawing.Size(865, 69);
            this.panelTop.TabIndex = 0;
            // 
            // useSslCheckBox
            // 
            this.useSslCheckBox.AutoSize = true;
            this.useSslCheckBox.Checked = true;
            this.useSslCheckBox.CheckState = System.Windows.Forms.CheckState.Checked;
            this.useSslCheckBox.Location = new System.Drawing.Point(23, 41);
            this.useSslCheckBox.Name = "useSslCheckBox";
            this.useSslCheckBox.Size = new System.Drawing.Size(66, 16);
            this.useSslCheckBox.TabIndex = 4;
            this.useSslCheckBox.Text = "Use SSL";
            this.useSslCheckBox.UseVisualStyleBackColor = true;
            // 
            // uidlButton
            // 
            this.uidlButton.Enabled = false;
            this.uidlButton.Location = new System.Drawing.Point(552, 45);
            this.uidlButton.Name = "uidlButton";
            this.uidlButton.Size = new System.Drawing.Size(98, 23);
            this.uidlButton.TabIndex = 6;
            this.uidlButton.Text = "UIDL";
            this.uidlButton.Click  = new System.EventHandler(this.UidlButtonClick);
            // 
            // totalMessagesTextBox
            // 
            this.totalMessagesTextBox.Location = new System.Drawing.Point(664, 32);
            this.totalMessagesTextBox.Name = "totalMessagesTextBox";
            this.totalMessagesTextBox.Size = new System.Drawing.Size(120, 21);
            this.totalMessagesTextBox.TabIndex = 7;
            // 
            // labelTotalMessages
            // 
            this.labelTotalMessages.Location = new System.Drawing.Point(664, 8);
            this.labelTotalMessages.Name = "labelTotalMessages";
            this.labelTotalMessages.Size = new System.Drawing.Size(120, 24);
            this.labelTotalMessages.TabIndex = 9;
            this.labelTotalMessages.Text = "Total Messages";
            // 
            // labelPassword
            // 
            this.labelPassword.Location = new System.Drawing.Point(317, 39);
            this.labelPassword.Name = "labelPassword";
            this.labelPassword.Size = new System.Drawing.Size(77, 25);
            this.labelPassword.TabIndex = 8;
            this.labelPassword.Text = "Password";
            // 
            // passwordTextBox
            // 
            this.passwordTextBox.Location = new System.Drawing.Point(394, 39);
            this.passwordTextBox.Name = "passwordTextBox";
            this.passwordTextBox.PasswordChar = '*';
            this.passwordTextBox.Size = new System.Drawing.Size(153, 21);
            this.passwordTextBox.TabIndex = 2;
            // 
            // labelUsername
            // 
            this.labelUsername.Location = new System.Drawing.Point(317, 5);
            this.labelUsername.Name = "labelUsername";
            this.labelUsername.Size = new System.Drawing.Size(77, 25);
            this.labelUsername.TabIndex = 6;
            this.labelUsername.Text = "Username";
            // 
            // loginTextBox
            // 
            this.loginTextBox.Location = new System.Drawing.Point(394, 5);
            this.loginTextBox.Name = "loginTextBox";
            this.loginTextBox.Size = new System.Drawing.Size(153, 21);
            this.loginTextBox.TabIndex = 1;
            // 
            // connectAndRetrieveButton
            // 
            this.connectAndRetrieveButton.Location = new System.Drawing.Point(552, 0);
            this.connectAndRetrieveButton.Name = "connectAndRetrieveButton";
            this.connectAndRetrieveButton.Size = new System.Drawing.Size(98, 42);
            this.connectAndRetrieveButton.TabIndex = 5;
            this.connectAndRetrieveButton.Text = "Connect and Retreive";
            this.connectAndRetrieveButton.Click  = new System.EventHandler(this.ConnectAndRetrieveButtonClick);
            // 
            // labelServerPort
            // 
            this.labelServerPort.Location = new System.Drawing.Point(116, 42);
            this.labelServerPort.Name = "labelServerPort";
            this.labelServerPort.Size = new System.Drawing.Size(38, 25);
            this.labelServerPort.TabIndex = 3;
            this.labelServerPort.Text = "Port";
            // 
            // portTextBox
            // 
            this.portTextBox.Location = new System.Drawing.Point(154, 42);
            this.portTextBox.Name = "portTextBox";
            this.portTextBox.Size = new System.Drawing.Size(153, 21);
            this.portTextBox.TabIndex = 3;
            this.portTextBox.Text = "110";
            // 
            // labelServerAddress
            // 
            this.labelServerAddress.Location = new System.Drawing.Point(19, 9);
            this.labelServerAddress.Name = "labelServerAddress";
            this.labelServerAddress.Size = new System.Drawing.Size(135, 24);
            this.labelServerAddress.TabIndex = 1;
            this.labelServerAddress.Text = "POP Server Address";
            // 
            // popServerTextBox
            // 
            this.popServerTextBox.Location = new System.Drawing.Point(154, 9);
            this.popServerTextBox.Name = "popServerTextBox";
            this.popServerTextBox.ScrollBars = System.Windows.Forms.ScrollBars.Horizontal;
            this.popServerTextBox.Size = new System.Drawing.Size(153, 21);
            this.popServerTextBox.TabIndex = 0;
            // 
            // panelProperties
            // 
            this.panelProperties.Controls.Add(this.gridHeaders);
            this.panelProperties.Dock = System.Windows.Forms.DockStyle.Bottom;
            this.panelProperties.Location = new System.Drawing.Point(0, 246);
            this.panelProperties.Name = "panelProperties";
            this.panelProperties.Size = new System.Drawing.Size(865, 198);
            this.panelProperties.TabIndex = 1;
            // 
            // gridHeaders
            // 
            this.gridHeaders.Anchor = ((System.Windows.Forms.AnchorStyles)((((System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Bottom) 
            | System.Windows.Forms.AnchorStyles.Left) 
            | System.Windows.Forms.AnchorStyles.Right)));
            this.gridHeaders.DataMember = "";
            this.gridHeaders.HeaderForeColor = System.Drawing.SystemColors.ControlText;
            this.gridHeaders.Location = new System.Drawing.Point(0, 0);
            this.gridHeaders.Name = "gridHeaders";
            this.gridHeaders.PreferredColumnWidth = 400;
            this.gridHeaders.ReadOnly = true;
            this.gridHeaders.Size = new System.Drawing.Size(865, 202);
            this.gridHeaders.TabIndex = 3;
            // 
            // panelMiddle
            // 
            this.panelMiddle.Controls.Add(this.panelMessageBody);
            this.panelMiddle.Controls.Add(this.panelMessagesView);
            this.panelMiddle.Controls.Add(this.attachmentPanel);
            this.panelMiddle.Dock = System.Windows.Forms.DockStyle.Fill;
            this.panelMiddle.Location = new System.Drawing.Point(0, 69);
            this.panelMiddle.Name = "panelMiddle";
            this.panelMiddle.Size = new System.Drawing.Size(865, 177);
            this.panelMiddle.TabIndex = 2;
            // 
            // panelMessageBody
            // 
            this.panelMessageBody.Controls.Add(this.progressBar);
            this.panelMessageBody.Controls.Add(this.messageTextBox);
            this.panelMessageBody.Controls.Add(this.labelMessageBody);
            this.panelMessageBody.Dock = System.Windows.Forms.DockStyle.Fill;
            this.panelMessageBody.Location = new System.Drawing.Point(337, 0);
            this.panelMessageBody.Name = "panelMessageBody";
            this.panelMessageBody.Size = new System.Drawing.Size(278, 177);
            this.panelMessageBody.TabIndex = 6;
            // 
            // progressBar
            // 
            this.progressBar.Anchor = ((System.Windows.Forms.AnchorStyles)(((System.Windows.Forms.AnchorStyles.Bottom | System.Windows.Forms.AnchorStyles.Left) 
            | System.Windows.Forms.AnchorStyles.Right)));
            this.progressBar.Location = new System.Drawing.Point(8, 151);
            this.progressBar.Name = "progressBar";
            this.progressBar.Size = new System.Drawing.Size(259, 13);
            this.progressBar.TabIndex = 10;
            // 
            // messageTextBox
            // 
            this.messageTextBox.Anchor = ((System.Windows.Forms.AnchorStyles)((((System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Bottom) 
            | System.Windows.Forms.AnchorStyles.Left) 
            | System.Windows.Forms.AnchorStyles.Right)));
            this.messageTextBox.Location = new System.Drawing.Point(8, 24);
            this.messageTextBox.MaxLength = 999999999;
            this.messageTextBox.Multiline = true;
            this.messageTextBox.Name = "messageTextBox";
            this.messageTextBox.ScrollBars = System.Windows.Forms.ScrollBars.Both;
            this.messageTextBox.Size = new System.Drawing.Size(259, 120);
            this.messageTextBox.TabIndex = 9;
            // 
            // labelMessageBody
            // 
            this.labelMessageBody.Location = new System.Drawing.Point(10, 9);
            this.labelMessageBody.Name = "labelMessageBody";
            this.labelMessageBody.Size = new System.Drawing.Size(163, 17);
            this.labelMessageBody.TabIndex = 5;
            this.labelMessageBody.Text = "Message Body";
            // 
            // panelMessagesView
            // 
            this.panelMessagesView.Controls.Add(this.listMessages);
            this.panelMessagesView.Controls.Add(this.labelMessageNumber);
            this.panelMessagesView.Dock = System.Windows.Forms.DockStyle.Left;
            this.panelMessagesView.Location = new System.Drawing.Point(0, 0);
            this.panelMessagesView.Name = "panelMessagesView";
            this.panelMessagesView.Size = new System.Drawing.Size(337, 177);
            this.panelMessagesView.TabIndex = 5;
            // 
            // listMessages
            // 
            this.listMessages.Anchor = ((System.Windows.Forms.AnchorStyles)((((System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Bottom) 
            | System.Windows.Forms.AnchorStyles.Left) 
            | System.Windows.Forms.AnchorStyles.Right)));
            this.listMessages.ContextMenu = this.contextMenuMessages;
            this.listMessages.Location = new System.Drawing.Point(10, 26);
            this.listMessages.Name = "listMessages";
            this.listMessages.Size = new System.Drawing.Size(319, 138);
            this.listMessages.TabIndex = 8;
            this.listMessages.AfterSelect  = new System.Windows.Forms.TreeViewEventHandler(this.ListMessagesMessageSelected);
            // 
            // contextMenuMessages
            // 
            this.contextMenuMessages.MenuItems.AddRange(new System.Windows.Forms.MenuItem[] {
            this.menuDeleteMessage,
            this.menuViewSource});
            // 
            // menuDeleteMessage
            // 
            this.menuDeleteMessage.Index = 0;
            this.menuDeleteMessage.Text = "Delete Mail";
            this.menuDeleteMessage.Click  = new System.EventHandler(this.MenuDeleteMessageClick);
            // 
            // menuViewSource
            // 
            this.menuViewSource.Index = 1;
            this.menuViewSource.Text = "View source";
            this.menuViewSource.Click  = new System.EventHandler(this.MenuViewSourceClick);
            // 
            // labelMessageNumber
            // 
            this.labelMessageNumber.Location = new System.Drawing.Point(10, 9);
            this.labelMessageNumber.Name = "labelMessageNumber";
            this.labelMessageNumber.Size = new System.Drawing.Size(163, 17);
            this.labelMessageNumber.TabIndex = 1;
            this.labelMessageNumber.Text = "Messages";
            // 
            // attachmentPanel
            // 
            this.attachmentPanel.Controls.Add(this.listAttachments);
            this.attachmentPanel.Controls.Add(this.labelAttachments);
            this.attachmentPanel.Dock = System.Windows.Forms.DockStyle.Right;
            this.attachmentPanel.Location = new System.Drawing.Point(615, 0);
            this.attachmentPanel.Name = "attachmentPanel";
            this.attachmentPanel.Size = new System.Drawing.Size(250, 177);
            this.attachmentPanel.TabIndex = 4;
            this.attachmentPanel.Visible = false;
            // 
            // listAttachments
            // 
            this.listAttachments.Anchor = ((System.Windows.Forms.AnchorStyles)((((System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Bottom) 
            | System.Windows.Forms.AnchorStyles.Left) 
            | System.Windows.Forms.AnchorStyles.Right)));
            this.listAttachments.Location = new System.Drawing.Point(10, 26);
            this.listAttachments.Name = "listAttachments";
            this.listAttachments.ShowLines = false;
            this.listAttachments.ShowRootLines = false;
            this.listAttachments.Size = new System.Drawing.Size(230, 138);
            this.listAttachments.TabIndex = 10;
            this.listAttachments.AfterSelect  = new System.Windows.Forms.TreeViewEventHandler(this.ListAttachmentsAttachmentSelected);
            // 
            // labelAttachments
            // 
            this.labelAttachments.Location = new System.Drawing.Point(14, 9);
            this.labelAttachments.Name = "labelAttachments";
            this.labelAttachments.Size = new System.Drawing.Size(164, 17);
            this.labelAttachments.TabIndex = 3;
            this.labelAttachments.Text = "Attachments";
            // 
            // saveFile
            // 
            this.saveFile.Title = "Save Attachment";
            // 
            // TestForm
            // 
            this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
            this.ClientSize = new System.Drawing.Size(865, 444);
            this.Controls.Add(this.panelMiddle);
            this.Controls.Add(this.panelProperties);
            this.Controls.Add(this.panelTop);
            this.Icon = ((System.Drawing.Icon)(resources.GetObject("$this.Icon")));
            this.Name = "TestForm";
            this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
            this.Text = "OpenPOP.NET Test Application";
            this.WindowState = System.Windows.Forms.FormWindowState.Maximized;
            this.panelTop.ResumeLayout(false);
            this.panelTop.PerformLayout();
            this.panelProperties.ResumeLayout(false);
            ((System.ComponentModel.ISupportInitialize)(this.gridHeaders)).EndInit();
            this.panelMiddle.ResumeLayout(false);
            this.panelMessageBody.ResumeLayout(false);
            this.panelMessageBody.PerformLayout();
            this.panelMessagesView.ResumeLayout(false);
            this.attachmentPanel.ResumeLayout(false);
            this.ResumeLayout(false);

		}
		#endregion

		/// <summary>
		///   The main entry point for the application.
		/// </summary>
		[STAThread]
		private static void Main()
		{
			Application.Run(new TestForm());
		}

		private void ReceiveMails()
		{
			// Disable buttons while working
			connectAndRetrieveButton.Enabled = false;
			uidlButton.Enabled = false;
			progressBar.Value = 0;

			try
			{
				if (pop3Client.Connected)
					pop3Client.Disconnect();
				pop3Client.Connect(popServerTextBox.Text, int.Parse(portTextBox.Text), useSslCheckBox.Checked);
				pop3Client.Authenticate(loginTextBox.Text, passwordTextBox.Text);
				int count = pop3Client.GetMessageCount();
				totalMessagesTextBox.Text = count.ToString();
				messageTextBox.Text = "";
				messages.Clear();
				listMessages.Nodes.Clear();
				listAttachments.Nodes.Clear();

				int success = 0;
				int fail = 0;
				for (int i = count; i >= 1; i -= 1)
				{
					// Check if the form is closed while we are working. If so, abort
					if (IsDisposed)
						return;

					// Refresh the form while fetching emails
					// This will fix the "Application is not responding" problem
					Application.DoEvents();

					try
					{
						Message message = pop3Client.GetMessage(i);

						// Add the message to the dictionary from the messageNumber to the Message
						messages.Add(i, message);

						// Create a TreeNode tree that mimics the Message hierarchy
						TreeNode node = new TreeNodeBuilder().VisitMessage(message);

						// Set the Tag property to the messageNumber
						// We can use this to find the Message again later
						node.Tag = i;

						// Show the built node in our list of messages
						listMessages.Nodes.Add(node);

						success  ;
					} catch (Exception e)
					{
						DefaultLogger.Log.LogError(
							"TestForm: Message fetching failed: "   e.Message   "\r\n" 
							"Stack trace:\r\n"  
							e.StackTrace);
						fail  ;
					}

					progressBar.Value = (int)(((double)(count-i)/count) * 100);
				}

				MessageBox.Show(this, "Mail received!\nSuccesses: "   success   "\nFailed: "   fail, "Message fetching done");

				if(fail > 0)
				{
					MessageBox.Show(this,
					                "Since some of the emails were not parsed correctly (exceptions were thrown)\r\n"  
					                "please consider sending your log file to the developer for fixing.\r\n"  
					                "If you are able to include any extra information, please do so.",
					                "Help improve OpenPop!");
				}
			} catch (InvalidLoginException)
			{
				MessageBox.Show(this, "The server did not accept the user credentials!", "POP3 Server Authentication");
			} catch (PopServerNotFoundException)
			{
				MessageBox.Show(this, "The server could not be found", "POP3 Retrieval");
			} catch(PopServerLockedException)
			{
				MessageBox.Show(this, "The mailbox is locked. It might be in use or under maintenance. Are you connected elsewhere?", "POP3 Account Locked");
			} catch (LoginDelayException)
			{
				MessageBox.Show(this, "Login not allowed. Server enforces delay between logins. Have you connected recently?", "POP3 Account Login Delay");
			} catch (Exception e)
			{
				MessageBox.Show(this, "Error occurred retrieving mail. "   e.Message, "POP3 Retrieval");
			} finally
			{
				// Enable the buttons again
				connectAndRetrieveButton.Enabled = true;
				uidlButton.Enabled = true;
				progressBar.Value = 100;
			}
		}

		private void ConnectAndRetrieveButtonClick(object sender, EventArgs e)
		{
			ReceiveMails();
		}

		private void ListMessagesMessageSelected(object sender, TreeViewEventArgs e)
		{
			// Fetch out the selected message
			Message message = messages[GetMessageNumberFromSelectedNode(listMessages.SelectedNode)];

			// If the selected node contains a MessagePart and we can display the contents - display them
			if (listMessages.SelectedNode.Tag is MessagePart)
			{
				MessagePart selectedMessagePart = (MessagePart)listMessages.SelectedNode.Tag;
				if (selectedMessagePart.IsText)
				{
					// We can show text MessageParts
					messageTextBox.Text = selectedMessagePart.GetBodyAsText();
				}
				else
				{
					// We are not able to show non-text MessageParts (MultiPart messages, images, pdf's ...)
					messageTextBox.Text = "<<OpenPop>> Cannot show this part of the email. It is not text <<OpenPop>>";
				}
			}
			else
			{
				// If the selected node is not a subnode and therefore does not
				// have a MessagePart in it's Tag property, we genericly find some content to show

				// Find the first text/plain version
				MessagePart plainTextPart = message.FindFirstPlainTextVersion();
				if (plainTextPart != null)
				{
					// The message had a text/plain version - show that one
					messageTextBox.Text = plainTextPart.GetBodyAsText();
				} else
				{
					// Try to find a body to show in some of the other text versions
					List<MessagePart> textVersions = message.FindAllTextVersions();
					if (textVersions.Count >= 1)
						messageTextBox.Text = textVersions[0].GetBodyAsText();
					else
						messageTextBox.Text = "<<OpenPop>> Cannot find a text version body in this message to show <<OpenPop>>";
				}
			}

			// Clear the attachment list from any previus shown attachments
			listAttachments.Nodes.Clear();

			// Build up the attachment list
			List<MessagePart> attachments = message.FindAllAttachments();
			foreach (MessagePart attachment in attachments)
			{
				// Add the attachment to the list of attachments
				TreeNode addedNode = listAttachments.Nodes.Add((attachment.FileName));

				// Keep a reference to the attachment in the Tag property
				addedNode.Tag = attachment;
			}

			// Only show that attachmentPanel if there is attachments in the message
			bool hadAttachments = attachments.Count > 0;
			attachmentPanel.Visible = hadAttachments;

			// Generate header table
			DataSet dataSet = new DataSet();
			DataTable table = dataSet.Tables.Add("Headers");
			table.Columns.Add("Header");
			table.Columns.Add("Value");

			DataRowCollection rows = table.Rows;

			// Add all known headers
			rows.Add(new object[] {"Content-Description", message.Headers.ContentDescription});
			rows.Add(new object[] {"Content-Id", message.Headers.ContentId});
			foreach (string keyword in message.Headers.Keywords) rows.Add(new object[] {"Keyword", keyword});
			foreach (RfcMailAddress dispositionNotificationTo in message.Headers.DispositionNotificationTo) rows.Add(new object[] {"Disposition-Notification-To", dispositionNotificationTo});
			foreach (Received received in message.Headers.Received) rows.Add(new object[] {"Received", received.Raw});
			rows.Add(new object[] {"Importance", message.Headers.Importance});
			rows.Add(new object[] {"Content-Transfer-Encoding", message.Headers.ContentTransferEncoding});
			foreach (RfcMailAddress cc in message.Headers.Cc) rows.Add(new object[] {"Cc", cc});
			foreach (RfcMailAddress bcc in message.Headers.Bcc) rows.Add(new object[] {"Bcc", bcc});
			foreach (RfcMailAddress to in message.Headers.To) rows.Add(new object[] { "To", to });
			rows.Add(new object[] {"From", message.Headers.From});
			rows.Add(new object[] {"Reply-To", message.Headers.ReplyTo});
			foreach (string inReplyTo in message.Headers.InReplyTo) rows.Add(new object[] {"In-Reply-To", inReplyTo});
			foreach (string reference in message.Headers.References) rows.Add(new object[] { "References", reference });
			rows.Add(new object[] {"Sender", message.Headers.Sender});
			rows.Add(new object[] {"Content-Type", message.Headers.ContentType});
			rows.Add(new object[] {"Content-Disposition", message.Headers.ContentDisposition});
			rows.Add(new object[] {"Date", message.Headers.Date});
			rows.Add(new object[] {"Date", message.Headers.DateSent});
			rows.Add(new object[] {"Message-Id", message.Headers.MessageId});
			rows.Add(new object[] {"Mime-Version", message.Headers.MimeVersion});
			rows.Add(new object[] {"Return-Path", message.Headers.ReturnPath});
			rows.Add(new object[] {"Subject", message.Headers.Subject});
			
			// Add all unknown headers
			foreach (string key in message.Headers.UnknownHeaders)
			{
				string[] values = message.Headers.UnknownHeaders.GetValues(key);
				if (values != null)
					foreach (string value in values)
					{
						rows.Add(new object[] {key, value});
					}
			}

			// Now set the headers displayed on the GUI to the header table we just generated
			gridHeaders.DataMember = table.TableName;
			gridHeaders.DataSource = dataSet;
		}

		/// <summary>
		/// Finds the MessageNumber of a Message given a <see cref="TreeNode"/> to search in.
		/// The root of this <see cref="TreeNode"/> should have the Tag property set to a int, which
		/// points into the <see cref="messages"/> dictionary.
		/// </summary>
		/// <param name="node">The <see cref="TreeNode"/> to look in. Cannot be <see langword="null"/>.</param>
		/// <returns>The found int</returns>
		private static int GetMessageNumberFromSelectedNode(TreeNode node)
		{
			if (node == null)
				throw new ArgumentNullException("node");

			// Check if we are at the root, by seeing if it has the Tag property set to an int
			if(node.Tag is int)
			{
				return (int) node.Tag;
			}

			// Otherwise we are not at the root, move up the tree
			return GetMessageNumberFromSelectedNode(node.Parent);
		}

		private void ListAttachmentsAttachmentSelected(object sender, TreeViewEventArgs args)
		{
			// Fetch the attachment part which is currently selected
			MessagePart attachment = (MessagePart)listAttachments.SelectedNode.Tag;

			if (attachment != null)
			{
				saveFile.FileName = attachment.FileName;
				DialogResult result = saveFile.ShowDialog();
				if (result != DialogResult.OK)
					return;

				// Now we want to save the attachment
				FileInfo file = new FileInfo(saveFile.FileName);

				// Check if the file already exists
				if(file.Exists)
				{
					// User was asked when he chose the file, if he wanted to overwrite it
					// Therefore, when we get to here, it is okay to delete the file
					file.Delete();
				}

				// Lets try to save to the file
				try
				{
					attachment.Save(file);

					MessageBox.Show(this, "Attachment saved successfully");
				} catch (Exception e)
				{
					MessageBox.Show(this, "Attachment saving failed. Exception message: "   e.Message);
				}
			}
			else
			{
				MessageBox.Show(this, "Attachment object was null!");
			}
		}

		private void MenuDeleteMessageClick(object sender, EventArgs e)
		{
			if (listMessages.SelectedNode != null)
			{
				DialogResult drRet = MessageBox.Show(this, "Are you sure to delete the email?", "Delete email", MessageBoxButtons.YesNo);
				if (drRet == DialogResult.Yes)
				{
					int messageNumber = GetMessageNumberFromSelectedNode(listMessages.SelectedNode);
					pop3Client.DeleteMessage(messageNumber);

					listMessages.Nodes[messageNumber].Remove();

					drRet = MessageBox.Show(this, "Do you want to receive email again (this will commit your changes)?", "Receive email", MessageBoxButtons.YesNo);
					if (drRet == DialogResult.Yes)
						ReceiveMails();
				}
			}
		}

		private void UidlButtonClick(object sender, EventArgs e)
		{
			List<string> uids = pop3Client.GetMessageUids();

			StringBuilder stringBuilder = new StringBuilder();
			stringBuilder.Append("UIDL:");
			stringBuilder.Append("\r\n");
			foreach (string uid in uids)
			{
				stringBuilder.Append(uid);
				stringBuilder.Append("\r\n");
			}

			messageTextBox.Text = stringBuilder.ToString();
		}

		private void MenuViewSourceClick(object sender, EventArgs e)
		{
			
			if (listMessages.SelectedNode != null)
			{
				int messageNumber = GetMessageNumberFromSelectedNode(listMessages.SelectedNode);
				Message m = messages[messageNumber];

				// We do not know the encoding of the full message - and the parts could be differently
				// encoded. Therefore we take a choice of simply using US-ASCII encoding on the raw bytes
				// to get the source code for the message. Any bytes not in th US-ASCII encoding, will then be
				// turned into question marks "?"
				ShowSourceForm sourceForm = new ShowSourceForm(Encoding.ASCII.GetString(m.RawMessage));
				sourceForm.ShowDialog();
			}
		}
	}
}