Hosting decided (spec App. D §D.1 option A): Stalwart on the QNAP, receiving and
sending directly; addresses @ultimo.email; mail apps allowed with app
passwords; mail host mail.ultimo.email. docs/mail-server-network.md records the
connection checks (clean IP, outbound 25 open, generic reverse DNS to change),
the router / Synology / QNAP port layout, container ports, TLS certificate,
the DNS records to set at home.pl, moving mail from home.pl, and checks after.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
