diff --git a/README.md b/README.md
index 43ee4af..5859eca 100644
--- a/README.md
+++ b/README.md
@@ -40,6 +40,12 @@ mysql:
     - MYSQL_PASSWORD=pdnspw
 ```
 
+## Environment Variables Supported
+
+Any setting from https://doc.powerdns.com/3/authoritative/settings/ is supported. Just add the prefix "PDNS\_" and replace any hyphens (-) with underscore (\_). Example: 
+
+``` allow-axfr-ips ===> PDNS\_ALLOW\_AXFR\_IPS ```
+
 ## Running
 
 ```