diff --git a/target/start-mailserver.sh b/target/start-mailserver.sh
index 37859b28..10198b71 100644
--- a/target/start-mailserver.sh
+++ b/target/start-mailserver.sh
@@ -203,7 +203,7 @@ touch /etc/postfix/vmailbox && postmap /etc/postfix/vmailbox
 touch /etc/postfix/virtual && postmap /etc/postfix/virtual
 
 #
-# Override Postfix configuration
+# Override Postfix configuration: main.cf
 #
 if [ -f /tmp/docker-mailserver/postfix-main.cf ]; then
   while read line; do
@@ -214,6 +214,18 @@ else
   echo "No extra postfix settings loaded because optional '/tmp/docker-mailserver/postfix-main.cf' not provided."
 fi
 
+#
+# Override Postfix configuration: master.cf
+#
+if [ -f /tmp/docker-mailserver/postfix-master.cf ]; then
+  while read line; do
+    postconf -M "$line"
+  done < /tmp/docker-mailserver/postfix-master.cf
+  echo "Loaded 'config/postfix-master.cf'"
+else
+  echo "No extra postfix settings loaded because optional '/tmp/docker-mailserver/postfix-master.cf' not provided."
+fi
+
 # Support general SASL password
 rm -f /etc/postfix/sasl_passwd
 if [ ! -z "$SASL_PASSWD" ]; then