hiiiiiiiiiii,
i was written the code like that,

string from = "[email protected]";
string to = "[email protected]";
string subject = "testing";
string body = "smtp tested";
MailMessage message = new MailMessage(from, to, subject , body);
SmtpClient emailClient = new SmtpClient("smtp.gmail.com", 587);
System.Net.NetworkCredential SMTPUserInfo = new System.Net.NetworkCredential("ssssssss","yyyyyyy");
emailClient.UseDefaultCredentials = false;
emailClient.Credentials = SMTPUserInfo;
emailClient.Send(message);
textBox1.Text = "Message Sent";


i got the error message "The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Must issue a STARTTLS command first 36sm6260958nza".
if anybody know how to rectify the problem. plz reply.