Unable to read data from the transport connection: net_io_connectionclosed

Unable to read data from the transport connection: net_io_connectionclosed

I'm getting this error when I send email using C#. My code is below, for reference. I am able to send email using Windows Live Mail from the same machine, though. What am I doing wrong? Thanks for your help!

ERROR: Unable to read data from the transport connection: net_io_connectionclosed

CODE:

var message = new MailMessage ("<my-zoho-email>", toAddress, subject, body);

message.IsBodyHtml = true ;

var client = new SmtpClient ( "smtp.zoho.com" , 465);

client.Credentials = new NetworkCredential ("<my-zoho-email>", "<my-zoho-password>");

client.EnableSsl = true ;

client.Send(message);