Add the ability to customize the Postfix master configuration

postfix/start.sh

@@ -5,7 +5,7 @@ for VARIABLE in `env | cut -f1 -d=`; do
   sed -i "s={{ $VARIABLE }}=${!VARIABLE}=g" /etc/postfix/*.cf
 done
 
-# Override Postfix configuration
+# Override Postfix main configuration
 if [ -f /overrides/postfix.cf ]; then
   while read line; do
     postconf -e "$line"
@@ -15,6 +15,16 @@ else
   echo "No extra postfix settings loaded because optional '/overrides/postfix.cf' not provided."
 fi
 
+# Override Postfix master configuration
+if [ -f /overrides/master.cf ]; then
+  while read line; do
+    postconf -M "$line"
+  done < /overrides/master.cf
+  echo "Loaded '/overrides/master.cf'"
+else
+  echo "No extra postfix settings loaded because optional '/overrides/master.cf' not provided."
+fi
+
 # Include table-map files
 if ls -A /overrides/*.map 1> /dev/null 2>&1; then
   cp /overrides/*.map /etc/postfix/