发邮件

System.Web.Mail.MailMessage Mailer = new System.Web.Mail.MailMessage();
Mailer.From = "[email protected]";
Mailer.To = "[email protected]";
Mailer.Subject ="发送测试";
Mailer.Body= "11111111111111111111111111111";
Mailer.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate", "1");
Mailer.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendusername", "xxx");
Mailer.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendpassword", "xxxx");
SmtpMail.SmtpServer = "smtp.sina.com.cn";
SmtpMail.Send(Mailer);

网址
http://www.codeproject.com/useritems/SendMailUsingGmailAccount.asp
更多的内容看，
http://systemwebmail.com/
http://www.systemnetmail.com/