Is there a way to greylist nothing except …? It looks like you can whitelist with a regex but not do the inverse of that.
I’ve used greylisting a while back but found issues with it (on shared hosting this was, not postgrey). I’m a bit wary of using now. Plus, the default whitelist doesn’t seems to have a regular update so I’d be concerned about that becoming out of date.
I have most of the spam under control with a few postfix settings to check hostname has reverse looking and checking hostname/IP in spamhaus blacklists. But looking at the spam that gets through I’m getting a lot from 198.23.153.x . If I check with mxtoolbox straight away then the IP is clean but check back later and it is dirty. And the X keeps increasing too, so 1st spam will be from 22.214.171.124, next from .36, next from .37 etc… Hence I was wondering about setting up greylisting to delay 198.23.153.* long enough for the blacklists to have caught up but leaving everything else alone.