Use network between services.

docker-compose_solr_traefik.yml

@@ -15,6 +15,7 @@ services:
       - solr
     networks:
       - traefik-public
+      - mailarch-network
     labels:
       # Create TCP endpoint in Traefik called "imaps" on port 993
       # Traefik will do the TLS part and forward it plaintext to 143 here
@@ -33,6 +34,8 @@ services:
     environment:
       LANG: C.UTF-8
       SOLR_SSL_ENABLED: "false"
+    networks:
+      - mailarch-network
     volumes:
       - /opt/docker/dovecot/solr/var-solr:/var/solr
       - /opt/docker/dovecot/solr:/setupdata
@@ -42,3 +45,5 @@ services:
 networks:
   traefik-public:
     external: true
+  mailarch-network:
+    attachable: true