make inet_protocol configurable

.env.example

@@ -40,3 +40,6 @@
 
 # Optional: This will use allow you to set a custom $message_size_limit value. Default is 10240000.
 #MESSAGE_SIZE_LIMIT=
+
+# Optional: This will let you decide which ip-protocol should be used.
+#INET_PROTOCOL=[ipv4|ipv6|all]

Dockerfile

@@ -10,7 +10,6 @@ RUN apk update --no-cache && \
     postfix && \
     mkdir -p /var/log/supervisor/ /var/run/supervisor/ && \
     sed -i -e 's/inet_interfaces = localhost/inet_interfaces = all/g' /etc/postfix/main.cf && \
-    sed -i -e 's/inet_protocols = all/inet_protocols = ipv4/g' /etc/postfix/main.cf && \
     chmod +x /run.sh && \
     newaliases
 

run.sh

@@ -120,6 +120,13 @@ if [ ! -z "${MESSAGE_SIZE_LIMIT}" ]; then
   echo "Setting configuration option message_size_limit with value: ${MESSAGE_SIZE_LIMIT}"
 fi
 
+# Set inet_protocol
+if [ ! -z "${INET_PROTOCOL}" ]; then
+  sed -i -e 's/inet_protocols = all/inet_protocols = ipv4/g' /etc/postfix/main.cf
+  echo "Setting configuration option inet_protocols with value: ${INET_PROTOCOL}"
+fi
+
+
 #Start services
 
 # If host mounting /var/spool/postfix, we need to delete old pid file before