If I want to send unlimited emails from my domain (not 500 max or 2000 per day) and I don't want to worry about hacks AND don't want to pay for overages, simple shared hosting is the (cheapest) way!?
I know of no shared-hosting provider that doesn't throttle emails. The minute you're talking more than about 200 an hour, you're going to either host your own mail server or route through any of the dozens of commercial SMTP providers.
It might be cheap but depending on the reputation of the hoster your e-mails will be hit or miss.