How Does "Mass Emailing" Work?

Okay i'm trying to wrap my head around this.
From what i understand you require an smtp server with a domain to send emails.
This smtp server has it's own ip (Does it matter if the ip changes?)
With this smtp server you can send a zillion emails out there is no limitation, except perhaps for hosting providers?

Big email services like yahoo gmail etc. Build trust with smtp servers, if a new smtp server pops up and it sends out a zillion emails it's flagged as spam. Perhaps there are other services designed specifically to watch for email spam ?

This requires the smtp sending out emails to "build trust" over time.

Am i missing anything?

Interesting stuff. I know ppl who offer mass spam service with no "spam" tag but I don't know where to get valid email databases.