Message history – if enabled – takes all messages you send through Yahoo! Messenger and archives them in your Yahoo! account on Yahoo! servers.

You can access and search your message history from any computer. This is nice for picking up conversations, or for remembering what you said. The search function is an amazing tool for finding something that was said, fast.

A note: Remember, whether or not you choose to enable this feature, your contacts may use Message History (or some other archiving feature).