public static void Run()
        {
            Pop3Client client = new Pop3Client();

            client.Host            = "pop.gmail.com";
            client.Port            = 995;
            client.SecurityOptions = SecurityOptions.SSLImplicit;
            client.Username        = "******";
            client.Password        = "******";

            try
            {
                // ExStart:ListMessagesAsynchronouslyWithMailQuery
                MailQueryBuilder builder = new MailQueryBuilder();
                builder.Subject.Contains("Subject");
                MailQuery    query                 = builder.GetQuery();
                IAsyncResult asyncResult           = client.BeginListMessages(query);
                Pop3MessageInfoCollection messages = client.EndListMessages(asyncResult);
                // ExEnd:ListMessagesAsynchronouslyWithMailQuery
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
        }