A practical outbound-only SMTP relay on a VPS: IP reputation checks, TCP 25, PTR/rDNS, Postfix, OpenDKIM, DNS authentication, an HTTP relay, queueing, systemd, gateway auth, validation, and rollback.
A practical outbound-only SMTP relay on a VPS: IP reputation checks, TCP 25, PTR/rDNS, Postfix, OpenDKIM, DNS authentication, an HTTP relay, queueing, systemd, gateway auth, validation, and rollback.