Can't use Gmail POP mail Thunderbird mail client-saying Less secure app

[pravin_01]

Hi,
I have Thunderbird mail client, running many gmail account and few other mail provider. Everything is working good from long time but recently one of my account with gmail won't work with Thunderbird mail client. Mozilla thunderbird gives me error that "password sending failed" , weblogin is required. And when I login to Gmail webmail, it all works good.

I tried changing password but I think its not about password but some other issue. Because I saw this mail :

	Review blocked sign-in attempt	
		
Hi Praveen Ranjan,

Google just blocked someone from signing into your Google Account pra*****@gmail.com from an app that may put your account at risk.
	Less secure app
Tuesday, April 3, 2018 6:17 PM (India Time)
Uttar Pradesh, India*
Don't recognize this activity?

If you didn't recently receive an error while trying to access a Google service, like Gmail, from a non-Google application, someone may have your password.

SECURE YOUR ACCOUNT


Are you the one who tried signing in?
Google will continue to block sign-in attempts from the app you're using because it has known security problems or is out of date. You can continue to use this app by allowing access to less secure apps, but this may leave your account vulnerable.

So, what could be problem, is it now Thunderbird is less secure , should I stop using Thunderbird or I can't access Gmail anymore with TB mail client ?