Hi Zygimantas,
That was a great hint to me. I checked the logs, and even though I had the less secure app settings on in my Gmail account, but still their server blocks my action. I log in to my Gmail account while I was on my cellular network, to introduce my SIM IP to the Gmail server as a secure address. And now it sends out an email every time the WAN status changes.
Thank you so much,
Navid