init.sls

{% from "opensmtpd/map.jinja" import opensmtpd with context %}

opensmtpd:
  pkg:
    - installed
    - pkgs: {{ opensmtpd.pkgs|json }}
  service:
    - running
    - name: {{ opensmtpd.service }}
    - require:
        - pkg: opensmtpd
  file.managed:
    - name: {{ opensmtpd.config }}/smtpd.conf
    - source: salt://opensmtpd/smtpd.conf.jinja
    - template: jinja
    - mode: 400
    - watch_in:
        - service: opensmtpd

secondary.conf.jinja

# Secondary mail server config
listen on {{ address }}
table relayed_domains { {{ domains }} }
accept from any for domain <relayed_domains> relay \
  backup {{ address }}

secondary.sls

{% from "opensmtpd/map.jinja" import opensmtpd with context %}
{% set secrets = pillar.get("opensmtpd_secrets", {}) %}

secondary:
  file.append:
    - name: {{ opensmtpd.config }}/smtpd.conf
    - source: salt://opensmtpd/secondary.conf.jinja
    - template: jinja
    - context:
        domains: {{ ", ".join(secrets.get('domains')) }}
        address: {{ secrets.get('address') }}
    - watch_in:
        - service: opensmtpd
    - require:
        - file: opensmtpd

smtpd.conf.jinja

# Default mail server config
listen on localhost
accept from local for local deliver to mbox