upgrade mail-server to v0.9.4

docker-compose.yml

@@ -56,9 +56,7 @@ services:
     labels:
       - "com.centurylinklabs.watchtower.enable=true"
   mail:
-    image: stalwartlabs/mail-server:v0.8.5
-    # build:
-    #   context: https://github.com/programmerjake/mail-server.git#fix-567
+    image: stalwartlabs/mail-server:v0.9.4
     restart: always
     expose:
       - '80'
@@ -75,7 +73,7 @@ services:
       - /usr/local/share/ca-certificates:/usr/local/share/ca-certificates:ro
     networks:
       - net_with_ipv6
-    # labels:
+    # labels:  # enable when mail-server has a stable release channel
     #   - "com.centurylinklabs.watchtower.enable=true"
 
 networks: