I don't agree with you. I run many, many small email setups and some rather large ones. I am based in the UK. The only thing that gets mail dropped big style

I don't agree with you. I run many, many small email setups and some rather large ones. I am based in the UK. The only thing that gets mail dropped big style these days, in my experience, is the saddest one: Reverse DNS entries, ie not getting PTR registered. This anachronism still seems to be a fixation by everyone. Content checkers seem to be pretty decent these days. My fav. is rspamd nowadays with Exim on the front. I generally wind back from doing anything fancy and leave it to defaults. Even more bizarrely, I do add a domain blacklist for all return addresses. As you know email addresses are easily fakeable but the semi legit spammers do stick to a list of domains and hence can be dropped with a few rules. They will go away after a while.