The withdrawal address whitelist is another security feature designed to make withdrawals safer. If the withdrawal whitelist function is turned on, your account will only be able to make withdrawals to the addresses that are whitelisted. In other words, you can block withdrawals to any address besides the address indicated by you.
You can use only one address for each currency. In order to activate Withdrawal Address Whitelist, please go to your account page/settings/addresses whitelist.
It is important to note that you can always add any other address to the whitelist. You simply need to change the settings. In this case, however, your withdrawals will be blocked for five days. If you attempt to withdraw funds during these days, you will be notified via email about temporary disablement. To change the settings, you will need to enter your 2FA code.
To conclude, if you turn on withdrawal whitelist function, you will always have an extra layer of security over your funds.
You can enable this function here