Update README.md

Author: variablenix

README.md

@@ -1,5 +1,5 @@
 # mail-infra
-Mail cluster diagram created with draw.io. Replicated Mail stores and replicated LDAP directory as a source for any of its lookups.
+Mail cluster diagram created with draw.io. Replicated Mail stores and replicated LDAP directory as a source for any of its lookups. 
 
 [MAIL INFRA DIAGRAM](https://github.com/KDN-Cloud/mail-infra/blob/main/Mail%20Diagram/pdf/Mail%20Diagram.pdf)
 
@@ -12,3 +12,5 @@ Mail cluster diagram created with draw.io. Replicated Mail stores and replicated
 * OpenLDAP
 * Cyrus SASL
 * Roundcube Webmail
+
+Directory source [LDAP Mail Schema](https://github.com/variablenix/ldap-mail-schema/blob/master/postfix-book.schema)