Installer: mail-gateway configure downstream smtp server addresses
diff --git a/charts/mail-gateway/templates/config.yaml b/charts/mail-gateway/templates/config.yaml
new file mode 100644
index 0000000..457f524
--- /dev/null
+++ b/charts/mail-gateway/templates/config.yaml
@@ -0,0 +1,144 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: maddy
+  namespace: {{ .Release.Namespace }}
+data:
+  smtp-servers.conf: |
+    maddy.{{ .Values.domains.primary.namespace}}.svc.cluster.local:587
+    {{ range .Values.domains.others}}
+    maddy.{{ .namespace }}.svc.cluster.local:587
+    {{ end }}
+  maddy.conf: |
+    $(hostname) = {{ .Values.domains.primary.mx }}
+    $(primary_domain) = {{ .Values.domains.primary.name }}
+    $(local_domains) = {{ .Values.domains.primary.name }}{{ range .Values.domains.others }} {{ .name }}{{ end }}
+
+    tls file /etc/maddy/certs/tls.crt /etc/maddy/certs/tls.key
+
+    auth.external authsmtp {
+        helper /usr/bin/auth-smtp
+        perdomain yes
+        domains $(local_domains)
+    }
+
+    hostname $(hostname)
+
+    msgpipeline local_routing {
+        destination {{ .Values.domains.primary.name }} {
+            deliver_to &{{ .Values.domains.primary.name }}
+        }
+        {{ range .Values.domains.others }}
+        destination {{ .name }} {
+            deliver_to &{{ .name }}
+        }
+        {{ end }}
+        default_destination {
+            reject 550 5.1.1 "User doesn't exist"
+        }
+    }
+
+    smtp tcp://0.0.0.0:25 {
+        insecure_auth no
+
+        defer_sender_reject yes
+
+        limits {
+            # Up to 20 msgs/sec across max. 10 SMTP connections.
+            all rate 20 1s
+            all concurrency 10
+        }
+
+        dmarc yes
+        check {
+            require_mx_record
+            dkim
+            spf
+        }
+
+        source $(local_domains) {
+            reject 501 5.1.8 "Use Submission for outgoing SMTP"
+        }
+        default_source {
+            destination $(local_domains) {
+                deliver_to &local_routing
+            }
+            default_destination {
+                reject 550 5.1.1 "User doesn't exist"
+            }
+        }
+    }
+
+    submission tls://0.0.0.0:465 tcp://0.0.0.0:587 {
+        auth &authsmtp
+        insecure_auth yes
+
+        defer_sender_reject yes
+
+        source $(local_domains) {
+            destination $(local_domains) {
+                deliver_to &local_routing
+            }
+            default_destination {
+                modify {
+                    dkim $(primary_domain) $(local_domains) default
+                }
+                deliver_to &remote_queue
+            }
+        }
+        default_source {
+            reject 501 5.1.8 "Non-local sender domain"
+        }
+    }
+
+    target.smtp {{ .Values.domains.primary.name }} {
+        hostname $(hostname)
+        attempt_starttls false
+        require_tls no
+        auth off
+        targets tcp://maddy.{{ .Values.domains.primary.namespace }}.svc.cluster.local:25
+    }
+
+    {{ range .Values.domains.others }}
+    target.smtp {{ .name }} {
+        hostname mail.{{ .name }}
+        attempt_starttls false
+        require_tls no
+        auth off
+        targets tcp://maddy.{{ .namespace }}.svc.cluster.local:25
+    }
+    {{ end }}
+
+    target.queue remote_queue {
+        target &outbound_delivery
+
+        autogenerated_msg_domain $(primary_domain)
+        bounce {
+            destination postmaster $(local_domains) {
+                deliver_to &local_routing
+            }
+            default_destination {
+                reject 550 5.0.0 "Refusing to send DSNs to non-local addresses"
+            }
+        }
+    }
+
+    target.remote outbound_delivery {
+        limits {
+            # Up to 20 msgs/sec across max. 10 SMTP connections
+            # for each recipient domain.
+            destination rate 20 1s
+            destination concurrency 10
+        }
+        mx_auth {
+            dane
+            mtasts {
+                cache fs
+                fs_dir mtasts_cache/
+            }
+            local_policy {
+                min_tls_level encrypted
+                min_mx_level none
+            }
+        }
+    }