I've searched for a case like yours and saw one (quoted below). Please note that this one was posted a month ago but still could help you have an idea on what to do or what you need just to change your email address. Click the link in the quote if you want to view the full conversation.
They replied to my ticket with this:
"The best way to change your email address is to create a new account and withdrawal your funds to that account.
If you no longer have access to your email address you will need to provide us with the new email address you would like to use. Please be aware that if you have already created an account with this new email address we will be unable to use the address and you will need to provide us with an unregistered email address.
Please see below for details on changing your email address. Email changes will have a minimum of 24 hours wait time for security purposes. Once 24 hours has passed and the email change has been approved it can take up to 1 week for the change to be put into place.
For Accounts valued under $1000 USD we will require the following information to verify ownership of your account.
1) Recent Balances 2) Recent Trades 3) Deposit/Withdrawal Transaction IDs 4) Recent ip addresses you have logged into
For Accounts valued at over $1000 USD we will also require the following forms of proof that you are the owner of the account:
1) Two forms of government identification and a selfie of you holding one of those identifications where we can match your face. Please also include a piece of paper with the word Bittrex written on it followed by today's date in your selfie.
The higher the account value, the more details we will require.
We understand this is a slow and painful way to recover your account, but we do this for both your safety and ours.
Best Regards,
Bittrex Support Team @ Bittrex Follow us on Twitter @
https://twitter.com/BittrexExchange"