If I wanted to spam people the way I get spammed, how would I do it?

I don’t want to. I’m just wondering how it’s done.

How do you get hold of a million active e-mail addresses and send messages to them all, at the same time?

One time I had to send out a group newsletter, and my account got suspended for suspicious activity because I sent out more than 50 messages at once.

How in particular do foreign spammers get all these U.S. addresses?

And if we know how it’s done, why can’t we shut them off?