Mailbox name not allowed. The server response was: sorry, Authentication failed or timed out. Please do get messages first to authenticate yourself.(#4.4.3)

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C#

please provide solution.. the code working fine on local system but when deployed on rediff server it throwing above exception message.

my c# code is:

public void sendEmail(string emailId, string emailBody)
{
try
{
MailMessage mailtocand;
mailtocand = new MailMessage();
mailtocand.From = new MailAddress("MyEmail");
mailtocand.To.Add(new MailAddress(emailId));
mailtocand.Subject = "Subject";
mailtocand.IsBodyHtml = true;

mailtocand.Body = emailBody;
SmtpClient smtpmailclient = new SmtpClient();
smtpmailclient.Host = "smtp.rediffmailpro.com";
smtpmailclient.Port = 25;
smtpmailclient.Timeout = 10000;
smtpmailclient.DeliveryMethod = SmtpDeliveryMethod.Network;
smtpmailclient.UseDefaultCredentials = false;
smtpmailclient.Credentials = new NetworkCredential("MyEmail", "Password");

smtpmailclient.Send(mailtocand);
}
catch (Exception ex)
{
Response.Write(ex.Message);
}

}