Today I received an email that someone else logged in on my bittrex account but in fact I haven't logged there for months, I don't know if there is a bug in their system so wanted to ask if anyone has received any similar email these days?
This is to notify you of a successful login to your account.
IP Address: (IPv6 not human readable)
User Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1453.93 Safari/537.36
this is a normal Email that bittrex (an many other places) send you whenever there is a "successful log in" to your account. this is a way of notifying you of all the activity on your account (read the first line of that email).
if you don't use bittrex anymore so you don't have to worry about anything.
it is possible that you have used a weak password or possibly similar password for another service that leaked your password to a hacker who tried to log in. so change your passwords immediately and never reuse same password on different places.