This guide shows how to self-host SMTP on a cheap VPS. It runs Dockerized Postfix and bundles opendkim for DKIM signing.
It skips IMAP and inbound SMTP and relies on registrar email forwarding. It configures reverse DNS plus SPF and DMARC DNS records.
It checks port 25 reachability, maps host port 1587 to container 587, and validates deliverability with Mail Tester and EasyDMARC.
