This is an example from MSDN:

MailMessage message = new MailMessage(
      "from@contoso.com",
      "to@contoso.com",
      "Subject.",
      "Body.");

SmtpClient client = new SmtpClient("localhost");
// Add credentials if the SMTP server requires them.
client.Credentials = CredentialCache.DefaultNetworkCredentials;
client.Send(message);

Bryan Phillips
MCSD, MCDBA, MCSE
Blog:  http://bphillips76.spaces.live.com