I did not receive this message, but when I wanted to deposit, I was asked to complete the identity verification. I tried entering random data and it was over. They did not ask me to send documents or proof of the information I provided, but I could not do anything without providing that data.
My new account limits are no deposit restrictions and a limit of about $5,000 for withdrawals per day.
I think this is what that is happening, but not an attack because they allow withdrawal, and also their ToS has been updated . I do not think I have used the exchange this year until last week that I used it for deposit and withdraw. Some days after, I got this email, which was yesterday. Stompix is correct.
If you intend to use this account in the future, enter your data, and I do not think that they will ask you to send files such as a passport photo or a selfie. If you do not intend to enter any random data.