private void SendEmail_Click(object sender, RoutedEventArgs e)
 {
     if (HostTextbox.Text == string.Empty)
     {
         System.Windows.MessageBox.Show("Please fill in the hosting provider.", "Error", MessageBoxButton.OK, MessageBoxImage.Warning);
         HostTextbox.Focus();
     }
     else if (EmailTextbox.Text == string.Empty)
     {
         System.Windows.MessageBox.Show("Please enter your email address.", "Error", MessageBoxButton.OK, MessageBoxImage.Warning);
         EmailTextbox.Focus();
     }
     else if (EmailTextbox.Text.Contains("@") == false)
     {
         System.Windows.MessageBox.Show("Please enter a valid email address.", "Error", MessageBoxButton.OK, MessageBoxImage.Warning);
         EmailTextbox.Focus();
     }
     else if (PasswordBox.Password == string.Empty)
     {
         System.Windows.MessageBox.Show("Please fill in your password.", "Error", MessageBoxButton.OK, MessageBoxImage.Warning);
         PasswordBox.Focus();
     }
     else if (EmailToTextbox.Text == string.Empty)
     {
         System.Windows.MessageBox.Show("Please Enter the email address where you want to send the mail.", "Error", MessageBoxButton.OK, MessageBoxImage.Warning);
         EmailToTextbox.Focus();
     }
     else if (EmailTextbox.Text.Contains("@") == false)
     {
         System.Windows.MessageBox.Show("Please enter a valid email address.", "Error", MessageBoxButton.OK, MessageBoxImage.Warning);
         EmailToTextbox.Focus();
     }
     else if (SubjectTextbox.Text == string.Empty)
     {
         System.Windows.MessageBox.Show("Please fill in the subject of your email.", "Error", MessageBoxButton.OK, MessageBoxImage.Warning);
         SubjectTextbox.Focus();
     }
     else if (MessageTextbox.Text == string.Empty)
     {
         System.Windows.MessageBox.Show("Please leave a message.", "Error", MessageBoxButton.OK, MessageBoxImage.Warning);
         MessageTextbox.Focus();
     }
     else
     {
         SendEmail.IsEnabled = false;
         if (HostTextbox.Text.StartsWith("pop3"))
         {
             HostTextbox.Text = HostTextbox.Text.Replace("pop3", "smtp");
         }
         else if (HostTextbox.Text.StartsWith("imap"))
         {
             HostTextbox.Text = HostTextbox.Text.Replace("imap", "smtp");
         }
         else if (!(HostTextbox.Text.Contains("smtp.")))
         {
             HostTextbox.Text = "smtp." + HostTextbox.Text;
         }
         ErrorFormat                = String.Empty;
         ErrorSmtp                  = String.Empty;
         Host                       = HostTextbox.Text;
         EmailFrom                  = EmailTextbox.Text;
         EmailTo                    = EmailToTextbox.Text;
         Password                   = PasswordBox.Password;
         Subject                    = SubjectTextbox.Text;
         Message                    = MessageTextbox.Text;
         AttachmentPath             = AttachmentTextbox.Text;
         StatusTextBlock.Foreground = Brushes.Black;
         StatusTextBlock.Text       = "Sending...";
         BackgroundWorker.RunWorkerAsync();
     }
 }
 private void SubjectTextbox_MouseDoubleClick(object sender, System.Windows.Input.MouseButtonEventArgs e)
 {
     SubjectTextbox.SelectAll();
 }