I have somehow accepted that it's impossible to distinguish a spammer and an earnest newcomer. There is only one metric of an honest mailserver and that is tim

I have somehow accepted that it's impossible to distinguish a spammer and an earnest newcomer. There is only one metric of an honest mailserver and that is time spent not blacklisted. This is true "proof of work" on behalf of the mail server admin. Running a mailserver on an IP range easily accessible to spammers (e.g. a cloud provider) gives you a negative start. You need to invest in "good IP addresses". I will gladly pay money to anyone who wants to do this. There are medium-sized players who deliver affordable, top-notch service. Turns out $5/mo. is enough for human service, because something that just works doesn't need a lot of it.