Mailbox unavailable exception plz help!!!

[jokerkachotabhai]

I am getting this error Mailbox unavailable. The server response was: 5.7.1 Unable to relay for niwant_gadgil@yahoo.co.in Following is the code which i have written : //////////////////////////////////////////////////////////////// protected void btnSubmit_Click(object sender, EventArgs e) { if (tbUsrName.Text == "") { Response.Write("<script language='javascript'>alert(\"UserName is Blank...\");</script>"); } else { try { string dbString = ConfigurationManager.ConnectionStrings["AppCon"].ConnectionString; SqlConnection sqlcon = new SqlConnection(dbString); sqlcon.Open(); SqlCommand sc = new SqlCommand("select usr_Email from usr_details where usr_ID = '" + tbUsrName.Text.ToString() + "'", sqlcon); SqlDataReader sqldr = sc.ExecuteReader(); if (sqldr.Read()) { string e_mail = sqldr["usr_Email"].ToString(); MailMessage msg = new MailMessage("noreplyadmin@learners21st.com", e_mail, "Password Recovery", "ur new password is 0a1b2c3d plz change it as soon as u log in"); SmtpClient mySmtp = new SmtpClient("localhost"); mySmtp.Send(msg); lblResult.Visible = true; lblResult.Text = "Submit occured"; } else { lblResult.Text = "No Such User Found........"; lblResult.Visible = true; } } catch (Exception ex) { lblResult.Visible = true; lblResult.Text = ex.Message; } } } NOTE : noreplyadmin@learners21st.com doesn't exist NOTE : I am not using ASPNETDB /////////////////////////////////////////////////////////// In web.config i hve included this section to post the mail <system.net> <mailSettings> <smtp> <network host="localhost" port="25" defaultCredentials="true"/> </smtp> </mailSettings> </system.net> How can i solve this plz help

[vinodkrebc]

pls put the host the local ip address like 192.168.0.54 instead of localhost and then try