I received following mail from Bittrex:
Thank you for being a valued customer of the Bittrex Global platform.
Per our protocols, we are required to obtain source of funds information from select users. Please fill out the form which you will find at --personalised link was here-- and submit it along with the respective supporting documents within 7 days in order to continue utilizing your Bittrex Global account. This is similar to what other cryptocurrency exchanges in regulated jurisdictions require.
Our privacy policies are available here: ---personalised link to their privacy policy--- which are part of our Terms of Service. Additionally, all of your personal information is kept on an encrypted server.
The link was to this pdf: (image taken from a post from another user on Reddit who received the same)
https://imgur.com/a/c86smPQI've barely used the account the past year, I think they try to disable inactive accounts to seize the assets.
The account was used more intensively before that and has been properly verified for at least 2 years.
The fact that they use personalised links is quite disturbing, I definitely won't be using Bittrex any longer.