I did not try to visit the link yet. So are you sure the mail comes from hitbtc officially? And these two email
It doesn't really matter so much since it's something that can be spoofed easily. I receive such emails regularly too, often from Chinese exchanges. I believe hackers with a list try to create an account and depending on the result it helps to identify an account.
The bot tries to create an account then
1) the site says "Registration successful, check out your email for bla bla bla"
2) the site says "wrong login information, bla bla bla"
If the bot sees case 2) it means you have an account, so to continue, the hackers will try to brute force the password. It's a way to clean their email lists.