Any email you receive from someone you’ve not corresponded to before should be opened cautiously.
If you were not expecting to receive an email from Bitflex or any other source, you should make sure that it comes from an official source and the right email address.
If you have received an unexpected device conformation email or 2FA authentication email from Bitflex, it means that your account has been compromised.
You should immediately change the password of your Bitflex account and your email account. Always use unique passwords that can’t be linked back to you.