Send mail error which previously worked

Hi there,

   Last month I have a bot which was able to send email to gmail. It worked perfectly. Yes, I had to run some configuration. However now same code does not work.

here is the code sample. 

using System;
using System.Linq;
using System.Collections.Generic;
using cAlgo.API;
using cAlgo.API.Indicators;
using cAlgo.API.Internals;
using cAlgo.Indicators;

namespace cAlgo.Robots
{
    [Robot(TimeZone = TimeZones.UTC, AccessRights = AccessRights.FullAccess)]
    public class Color : Robot
    {
        [Parameter("Periods ", DefaultValue = 0.0)]
        public int Periods { get; set; }

        bool Done;
        protected override void OnStart()
        {
            Done = false;
        }

        protected override void OnTick()
        {
            if(!Done)
            {
                Print("Send email");
                Notifications.SendEmail("mymail@gmail.com", "mymail@gmail.com", "from ctrader test", "mail body");
                Done = true;
            }
        }

        protected override void OnStop()
        {
            // Put your deinitialization logic here
        }
    }
}

here is error I have. 

Anything wrong with my code?

Thanks in advance

Noppanon