it seems only for EU (or GB too?)
or possible emails from the Ledger Leak from BittrexGlobal
(or some fishing sites)?
Then I should have been hit with it. Living in the EU now, and have been using Bittrex from here 90% of the time. Ledgerleaks I don't think so, OP and others received it legitimately.
My Account has been disabled because they are changes their KYC rules. I have been verified since 2017, and try to reopen my account few weeks ago to see my coin there. I'm surprised because I never get any email notification (I already try to search the notification maybe I missed it, but is no email about it) about this changes. From this case, I will not recommend Bittrex to anyone. If anyone have any asset there, it will better to withdraw it ASAP, and stay away from that exchange before too late.
I've had Proof of Funds requests, but not from Bittrex, which I'm fairly active at. Most recent transaction (bank wire) was first week of January. I barely get any news from them either, but probably because I'm not subscribed. I don't even get notifications when they disable wallets of certain crypto!