My email server is self hosted without DNS. I wonder if this service does work with IP literals: mailbox[x.x.x.x], mailbox[ipv6:....] or even mailbox@x.x.x....ip6.arpa

Because selling such email addresses is worth nothing to data brokers, then they kind of establish a trust relationship with this service, until they have a payment processor, but I don't know of a payment processor which is not gate by 'whatng cartel' web engines.