This article claims 1.8 billion users (though some people have more than one account):

https://techjury.net/blog/gmail-statistics/

> I would say closer to 70 million

I want to negotiate, but since you started with such a low number, it won't be worth it.

700 million people only from my country (India) would be a good start if you want to continue.

It’s probably closer to 70M but that’s probably absurdly off too. I bet there’s 70M people in the US alone who use Google services for valuable information. GMail alone is massive.