Do You Edit All Your Sites From The Same IP?

Black/grey/whitelisting is a common method to fight email spam, as is content analysis you're describing above. As far as I know it's got very little to do with search engine penalties and filtering. Why would it? You're talking about two completely different topics here, and I can see where the confusion comes from.

Of course you're welcome to believe what you want, but you'd need a better argument for me to even consider it.

Email spam is a constant battle for shared hosts because spammers themselves try to get in, and because sites get hacked. Professional hosts have systems in place to cut the spam after a short burst of activity. Yes, any shared server can end up on a blacklist because of this, but most big name hosts are pretty good at getting them out of there.

Again, I'm certain that Google knows this stuff better than you or I. Google is hosting one of the largest email services after all. And they've got their own filtering solution that's about as opaque as the search engine algorithm.

I'm not exactly a world-known expert in either of these, but I've sent some email and done some SEO. In my opinion email spam and spam-like search engine results do not have that much in common. Of course Google might take the IP address in account - we don't really know what they're up to - but the approach would be so naive that I can't see any reason why they'd do that.