I'd add that it's not just the reputation of your IP, but the reputation of your whole /24 block. That seems to be where a lot of filtering based on reputation takes place. I've got my corporate email server on a VPS (running FreeBSD with exim) with a hosting company that cares about its reputation (and charges a bit more for it) and email delivery is never a problem. I've also got a identically set up but personal email server on a crappy little cheap VPS which does have a static IP and hasn't had any spam on it for years, but plenty of other IPs in the /24 block get filthy with spam. My IP gets blacklisted quite frequently because of it.
> but the reputation of your whole /24 block. That seems to be where a lot of filtering based on reputation takes place.
That is due to the prevalence of what is known as Snowshoe Spam.
Spammers get old of (or infiltrate) large net blocks and then spread out their spamming across the entire range.
The extreme version of Snowshoe Spam is known as Hailstorm Spam. For fairly obvious reasons ... spammers get hold of (or infiltrate) a large netblock, intensively abuse the hell out of it and then move on.
That has been on a downward trend for some time thankfully, due to the way things work these days it's much easier and more reliable to hijack a vm or rent one with a stolen card, rpki, urpf and carrier verification means using thieved IP space is a lot of effort these days
I'd add that it's not just the reputation of your IP, but the reputation of your whole /24 block. That seems to be where a lot of filtering based on reputation takes place. I've got my corporate email server on a VPS (running FreeBSD with exim) with a hosting company that cares about its reputation (and charges a bit more for it) and email delivery is never a problem. I've also got a identically set up but personal email server on a crappy little cheap VPS which does have a static IP and hasn't had any spam on it for years, but plenty of other IPs in the /24 block get filthy with spam. My IP gets blacklisted quite frequently because of it.