I am getting an error message when sending an email through a contact form: "Mailbox unavailable. The server response was: No such user here" I have followed the example on the Winhost site with the following code: MailMessage message = newMailMessage(); message.From = newMailAddress("firstname.lastname@example.org"); message.To.Add("email@example.com"); //set the content message.Subject = "Request For Consultation"; StringBuilder sb = newStringBuilder(); sb.AppendLine("A request for a consultation has been sent through http://www.drguillotcosmeticsurgery.com."); sb.AppendLine(); sb.AppendLine("Name: " + name); sb.AppendLine("Email: " + email); sb.AppendLine("Comments: " + comments); message.Body = sb.ToString(); //send the message SmtpClient smtp = newSmtpClient("mail.drguillotcosmeticsurgery.com"); NetworkCredential Credentials = newNetworkCredential("firstname.lastname@example.org", "mypasswordwenthere"); smtp.Credentials = Credentials; smtp.Send(message); The postmaster email address is the default email so I know it exists. I've logged into CPanel and verified the email and logged into webmail with it. I also tried adding this to my web.config file: <system.net> <mailSettings> <smtp from="email@example.com"> <network host="mail.drguillotcosmeticsurgery.com" userName="firstname.lastname@example.org" password="mypasswordwenthere" defaultCredentials="true"/> </smtp> </mailSettings> </system.net> Can anyone explain what the issue is and how to get the form working? Thanks in advance.