Sending email from a form

I am trying to send email from a .net page. Here is the essential code for instatiating the mailmessage object and assigning it properties.
MailMessage mailmessage = new MailMessage();

mailmessage.To = "mailto:[email protected]";
mailmessage.From = txtName.Text;
mailmessage.Subject = "New entry in the Guest book";
mailmessage.BodyFormat = MailFormat.Text;
mailmessage.Body = tboxcomments.Text; ;

SmtpMail.Send(mailmessage);

When I submit the form I get the following error message
The "SendUsing" configuration value is invalid.
with the line SmtpMail.Send(mailmessage); highlighted. Anybody know what this error means? Do I need to configure something in order to send email?
Thanks,</font id="Arial">
Tim

 

Yep,

You need to set the value for the smtp server, which is "localhost".

 

Thanks!