SmtpPermissionAttribute
Controls access to Simple Mail Transport Protocol (SMTP) servers.
                using System.Security;
using System.Security.Permissions;
namespace System.Net.Mail
{
    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Constructor | AttributeTargets.Method, AllowMultiple = true, Inherited = false)]
    public sealed class SmtpPermissionAttribute : CodeAccessSecurityAttribute
    {
        public string Access {
            get {
                return null;
            }
            set {
            }
        }
        public SmtpPermissionAttribute(SecurityAction action)
            : base(action)
        {
        }
        public override IPermission CreatePermission()
        {
            return null;
        }
    }
}