Yeah, I got that, and while I am mildly worried about that, it hasn't been an issue in the last almost 20 years. I am only mentioning bandwidth because someone

Yeah, I got that, and while I am mildly worried about that, it hasn't been an issue in the last almost 20 years. I am only mentioning bandwidth because someone could easily saturate my internet connections by extensively brute forcing, and that's another mild concern (perhaps those are things that kill my modems?). In practice, biggest issue is that Gmail in particular will never rank your server as trusted because you are sending too low a volume (how's that for an anti spam measure?), and 1/3rd of recepients report emails ending up in spam folders. Curiously, only Gmail does that.