@Gargron @kev Hmm, yeah I understand that.. And I get that that's important. So what are the options to fight spam then?

(1) contact the spammer's server's admin
(2) ask your admin to block the spammer's entire domain

So (1) is obviously preferred. But it both demands a lot of energy from admins and it doesn't help if domains have loose policies or are intended for spam.

And (2) is actually similar to what I requested, just delegated to the server admin. The spammer's post can still exist.