This is a network related error. Your application cannot connect to the mail server specified

SmtpMail.SmtpServer

• Is a valid SMTP Server
• Check to be sure the server System.Web.Mail is executing on can connect to the mail server. Some times firewalls or proxy servers can get in the way.
• Try specifying the value by IP address. Poor DNS resolution can sometimes hinder name lookups.
• Make sure the that the mail server is running at port 25
.
• If you did not specify a SmtpMail.SmtpServer property, or if SmtpMail.SmtpServer points to "localhost" (or the equivalent), be sure the SMTP Service is running on port 25.
• For testing purposes change the MailMessage.From and MailMessage.To properties to an address that exists on SmtpMail.SmtpServer. Some times this exception is thrown, when it really is a relay issue.