nextcloud: Run an SMTP relay locally

For some reason, Nextcloud seems to have trouble sending mail via the
network-wide relay.  It opens a connection, then just sits there and
never sends anything until it times out.  This happens probably 4 out of
5 times it attempts to send e-mail messages.

Running Postfix locally and directing Nextcloud to send mail through it
and then on to the network-wide relay seems to work much more reliably.

group_vars/nextcloud.yml

@@ -10,7 +10,7 @@ nextcloud_trusted_domains:
 - '{{ ansible_fqdn }}'
 nextcloud_smtp:
   from: nextcloud@pyrocufflink.net
-  host: mail.pyrocufflink.blue
+  host: 127.0.0.1
   port: 25
 dnf_automatic_exclude: nextcloud
 
@@ -52,3 +52,8 @@ promtail_scrape_configs:
   - timestamp:
       source: timestamp
       format: '2006-01-02T15:04:05-0700'
+
+smtp:
+  mode: relay
+  host: mail.pyrocufflink.blue
+  port: 25

hosts

@@ -235,6 +235,9 @@ chromie.pyrocufflink.blue
 [smtp-relay]
 smtp1.pyrocufflink.blue
 
+[smtp-relay:children]
+nextcloud
+
 [squid]
 
 [sudo]