A few days ago, I got an email reporting that one of my online accounts has been accessed by a new IP Address. Someone used my email address and the account's (quite strong) password to access the online account.
I've checked whether my email address has been compromised using these websites: https://haveibeenpwned.com/ and https://hacked-emails.com/ and apparently my address has not been compromised.
How is this possible to know how someone got an access to my email address?
Should I change my email's password? Should I change an email address?