It is not from a single source but is a "combo list" —a curated compilation of data from thousands of older, individual breaches (e.g., LinkedIn, Dropbox, Yahoo).
The file is a sanitized data set commonly associated with large-scale credential leaks, most notably the massive "Collection #1" breach discovered in 2019. File Overview Email-Pass_joined_normalized_nodup.txt
Because the passwords in this specific file are often "normalized" into plain text, they are immediately usable without further decryption. It is not from a single source but
Hackers use these files to power automated bots that attempt to log into various websites using the leaked email/password combinations. Hackers use these files to power automated bots
Store unique, complex passwords for every site using tools like 1Password or NordPass .
Turn on multi-factor authentication (MFA) on all sensitive accounts to provide a secondary layer of protection even if your password is leaked.