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 xx.xxx.xx.xx:25

hi below msg show when  send auenthication mail
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 xx.xxx.xx.xx:25 i am using below code
MailMessage mail = new MailMessage();         MailMessage msg = new MailMessage();         msg.From = new MailAddress("test@ic.com", "ITest");         msg.To.Add("test@ic.com");         msg.Bcc.Add("sat@vmail.in");   msg.Subject = "[test.com]Feedback Form";         msg.IsBodyHtml = true;         msg.Body = "Dear Administrator,<br/>Det ...