Effective against slashing and even animal teeth. Chainmail is still used today by shark divers, butchers, fishermen and other professions which involve regular blade usage. Some German police forces wear chainmail as well.
The rings of steel compress on a point, when someone is hit they naturally move away from the blow which is enough to protect them. A lot of chainmail tests aren’t accurate since they hit a stationary dummy that is anchored to the ground. People aren’t anchored to the ground so it’s not a good representation of how effective chainmail is. Almost every culture in the past had their own form and styles of chainmail. Many cultures never met or crossed paths, but they had similar methods of weapons and armour, chainmail being one of them.