用smtpmail通过需要认证的smtp服务器发信

以前曾经碰到这个问题，没办法只好自己做了个类，用tcpclient建立连接，根据RFC821自己编码，差点没死掉。今天发现了更简单的办法！

MailMessage mail = new MailMessage();
mail.To = "me@mycompany.com";
mail.From = "you@yourcompany.com";
mail.Subject = "this is a test email.";
mail.Body = "Some text goes here";
mail.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate", "1"); //basic authentication
mail.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendusername", "my_username_here"); //set your username here
mail.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendpassword", "super_secret"); //set your password here
SmtpMail.SmtpServer = "mail.mycompany.com"; //your real server goes here
SmtpMail.Send( mail );