Gaining access to a Mail.com account is particularly dangerous because the email serves as the "master key" for resetting passwords on almost every other linked service.
Services like Have I Been Pwned track these specific file names and can notify you if your email appears in the "450K Mail.com" or similar leaks. 450K Mail.com Combolist.txt
Hackers infiltrate a website’s database and extract user credentials. Gaining access to a Mail