I've just received this scam email.

[ovcijisir]

The one thing that interests me is how much BTC did scammer collect this way

Did you check the balance on blockchain.info?

[cok_elat]

Those extortion emails were common several months ago. They included usernames and passwords (that they got from hacked web sites), so they seemed very convincing.

These scammers didn't provide any info to back up their claims, so it's probably just some script kiddies that are just spamming email lists. I would ignore it. Its not worth any more of your time.

I think this case is not just on e-mail, but a lot of it also happens to some social media and even messages or telephone calls