E-mail is not, in practice, a federated protocol which anyone can participate in. E-mail is, in practice, a protocol where Microsoft, Apple and Google can send mail between each others' systems.
That’s one problem I never had. With DKIM, SPF, and the other right DNS records in place, I had no worse trouble with deliverability in general than I do with a large host. Every couple of years I’d try to email someone with an rule like “don’t accept email from a VPS, at all, ever”, and shrug it off because they were already use to discarding a huge chunk of valid email so what’s one more.
E-mail is not, in practice, a federated protocol which anyone can participate in. E-mail is, in practice, a protocol where Microsoft, Apple and Google can send mail between each others' systems.
Stop using e-mail.