The "Kubernetes" subnet is a /27, not a /28. There are hosts in that
upper section that was masked out, and these were unable to send e-mails
via the relay because they were excluded from the `mynetworks` value.
AWS is going to begin charging extra for routable IPv4 addresses soon.
There's really no point in having a relay in the cloud anymore anyway,
since a) all outbound messages are sent via the local relay and b) no
messages are sent to anyone except me.
*smtp1.pyrocufflink.blue* is a VM that will replace
*smtp0.pyrocufflink.blue*, a Raspberry Pi.
I decided that there is little use in having the availability guarantee of
a discreet machine for the SMTP relay. The only system that would NEED
to send mail if the VM host fails is Zabbix, which operates as its own
relay anyway. As such, the main relay can be a VM, and the Raspberry Pi
can be repurposed as a recursive DNS server.
Dustin