Man it was a real artifact of time that I remember some email newsletters back on AOL where the writer would get mad and kick you off the list if you didn't reply to the newsletter thanking the author.
Back in the AOL days you would hang out in the Warez chat room, and you would subscribe to download files using email as the delivery. Chat for a few minutes and then next time you log in. You've got files!
For me it started in AOL, once banned for taking over the Disney chat I then learned about IRC and from there I learned of usenet. Been usenet ever since.