Activity on unused apple account

So before a few hours ago, i recieved a mail to a mail account i dont even remember a have an apple account linked to. Saying your mail has been changed. I checked my mail history and found out some mails regarding an apple account 11 years ago so probably i forgot i created it. I had no cards saved into it. What bothers me is the sudden activity. I dont remember any password so couldnt log in. i tried a couple wrong passwords and locked the account. So my questions are, is it possible to someone log in my account and change its mail address without a verification mail? And is there anything i can do regarding this issue except what i did which is locking the account via typing wrong passwords.