This is a network related error. Your application cannot connect to the mail server specified.
Make sure that the following are true about SmtpMail.SmtpServer:
- Is a valid SMTP Server
- Make sure that the server System.Web.Mail is running or 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 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.