> It is not. There's still a significant amount of spam that doesn't have SPF, there's a lot of forgery and it's easier to filter if everyone used the holy trinity.

Absolutely. But but again, this will _not_ solve SPAM as the parent implied.

> That's what you see on and from gmail, but it's not the majority of spam.

There's a huge variability on sources, depending also on the class of users you have on your server. However I do keep all copies of spam that could pass greylisting for classification purposes since the early 2010' from various sources and honeypot addresses -- correctly signed spam _is_ the vast majority.

Low-effort spammers are pretty easy to weed out. And while rejecting messages without SPF is still not feasible, it wouldn't _improve_ the ham/spam filtering ratio in my case.