gistfile1.cs

using System.Configuration;

namespace CustomConfigurationSection
{
    public class SmtpSettings : ConfigurationSection
    {
        [ConfigurationProperty("Url", DefaultValue = "smtp.returngis.com", IsRequired = true)]
        public string Url
        {
            get
            {
                return (string)this["Url"];
            }

            set
            {
                this["Url"] = value;
            }
        }

        [ConfigurationProperty("Port", DefaultValue = 80)]
        public int Port
        {
            get
            {
                return (int)this["Port"];
            }

            set
            {
                this["Port"] = value;
            }
        }

        public static SmtpSettings GetSettings() 
        {
            var settings = ConfigurationManager.GetSection("SmtpSettings") as SmtpSettings;
            return settings;
        }
    }
}