MessageSaver was a AOL Instant Messenger bot that I wrote in 2002 as a sort of “answering machine” when people were offline. Users could send a message to the MessageSaver account like tell JoeBob22 call me when you’re free, and when JoeBob22 came back online, MessageSaver would send them the message.
It was only online for a few months, but had around 10,000 users at its peak. It was mildly abused (as you could expect), but overall, it was pretty successful. It was the type of feature that was needed at the time.
For historical purposes, the MessageSaver source code can be downloaded here: