A combo list is a massive text file compiled from multiple data breaches across various websites. Unlike a "raw" database leak from a single site, a combo list is a curated collection designed for high-volume automated attacks.
If you received an alert that your email is part of a combo list, you should take immediate action: Combolists and ULP Files on the Dark Web - Group-IB Download 684K COMBO LIST UPDATE zip
: Usually simple text ( .txt ) where each line is a login pair. A combo list is a massive text file