procedure TForm1.Button1Click(Sender: TObject);   
const   
   POP3_OK = 1;   
begin   
   clPOP3.Server := 'mail.myserver.com';   
   clPOP3.UserName := 'test';   
   clPOP3.Password := 'test';   
   clPOP3.Open();   
 
   clPOP3.SendCommandSync('LIST', [POP3_OK]);   
   ShowMessage(clPOP3.Response.Text);   
 
   clPOP3.Close();   
end;