I'm not sure about unlimited addresses (probably not), but I've been using Zoho for this for free for years, and I'm pretty sure I set up accounts for my whole family, firstname@lastname.com (how many of them besides me actually used them, I don't know). Works pretty well. I'd guess it's probably limited to like 10 accounts or something, but that's been enough for me. If you (general) don't have quite the same need for unlimited accounts, I'd say it's a good sleeper pick.