Problem on Sending Mail on Live

using System.Net;
using System.Net.Mail;

string smtpAddress = "smtp.mail.yahoo.com";
int portNumber = 587;
bool enableSSL = true;

string emailFrom = "email@yahoo.com";
string password = "abcdefg";
string emailTo = "someone@domain.com";
string subject = "Hello";
string body = "Hello, I'm just writing this to say Hi!";

using (MailMessage mail = new MailMessage())
{
    mail.From = new MailAddress(emailFrom);
    mail.To.Add(emailTo);
    mail.Subject = subject;
    mail.Body = body;
    mail.IsBodyHtml = true;
    // Can set to false, if you are sending pure text.

    mail.Attachments.Add(new Attachment("C:\\SomeFile.txt"));
    mail.Attachments.Add(new Attachment("C:\\SomeZip.zip"));

    using (SmtpClient smtp = new SmtpClient(smtpAddress, portNumber))
    {
        smtp.Credentials = new NetworkCredential(emailFrom, password);
        smtp.EnableSsl = enableSSL;
        smtp.Send(mail);
    }
}