C# – The problem is about sending email in ASP.NET

protected void SendEmail(object sender, EventArgs e)
    {
        SmtpClient smtpClient = new SmtpClient();
        MailMessage message = new MailMessage();
        try
        {
            MailAddress fromAddress = new MailAddress("fromemail", "From Me");
            MailAddress toAddress = new MailAddress("toemail", "To You");
            message.From = fromAddress;
            message.To.Add(toAddress);
            message.Subject = "Testing!";
            message.Body = "This is the body of a sample message";
            smtpClient.Host = "smtp.host.com";
            smtpClient.Credentials = new System.Net.NetworkCredential("username", "password");
            smtpClient.EnableSsl = true;
            smtpClient.Port = 587;
            smtpClient.Send(message);
            statusLabel.Text = "Email sent.";
        }
        catch (Exception ex)
        {
            statusLabel.Text = "Coudn't send the message!\n"+ex.Message;
        }
    }

The error is

"Failure sending mail."

I can not send any.
What is the problem?

innerexception is

System.Net.WebException: Unable to connect to the remote server —> System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 74.125.39.109:587 at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress) at System.Net.Sockets.Socket.InternalConnect(EndPoint remoteEP) at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Int32 timeout, Exception& exception) — End of inner exception stack trace — at System.Net.ServicePoint.GetConnection(PooledStream PooledStream, Object owner, Boolean async, IPAddress& address, Socket& abortSocket, Socket& abortSocket6, Int32 timeout) at System.Net.PooledStream.Activate(Object owningObject, Boolean async, Int32 timeout, GeneralAsyncDelegate asyncCallback) at System.Net.PooledStream.Activate(Object owningObject, GeneralAsyncDelegate asyncCallback) at System.Net.ConnectionPool.GetConnection(Object owningObject, GeneralAsyncDelegate asyncCallback, Int32 creationTimeout) at System.Net.Mail.SmtpConnection.GetConnection(String host, Int32 port) at System.Net.Mail.SmtpTransport.GetConnection(String host, Int32 port) at System.Net.Mail.SmtpClient.GetConnection() at System.Net.Mail.SmtpClient.Send(MailMessage message)