//devo prima collegarmi al database ed impostare l'sql command
SqlDataReader aReader = cmd.ExecuteReader();
System.Web.Mail.MailMessage myMail = new System.Web.Mail.MailMessage();
myMail.From = "me@mydomain.com";
myMail.Body = "This is my e-mail message";
while ( aReader.Read() )
{
  myMail.To = aReader["Email"];
  System.Web.Mail.SmtpMail.Send(myMail);
}