README: additional usage instructions (#39)

related to haraka/Haraka#3369

README.md

@@ -1,6 +1,10 @@
 # WildDuck plugin for Haraka
 
-This plugin enables recipient checks for Haraka. The plugin normalizes recipient email addresses and validates these against the users table in the WildDuck database. It also checks quota usage, so if the user quota has already been exceeded, the message is rejected.
+This plugin:
+
+- enables recipient checks for Haraka. It normalizes recipient email addresses and validates these against the users table in the WildDuck database.
+- checks quota usage, so if the user quota has been exceeded, the message is rejected.
+- delivers messages to mongodb.
 
 ## Install
 
@@ -15,7 +19,7 @@ WildDuck plugin should be placed last in the plugins file.
 
 ### Configuration
 
-WildDuck plugin expects MongoDB settings to be set. By default, it uses unauthenticated localhost. If you need to use more specific settings then create your own configuration file
+This plugin expects MongoDB settings to be set. By default, it uses unauthenticated localhost. If you need to use more specific settings then create your own configuration file:
 
 ```sh
 cp node_modules/haraka-plugin-wildduck/config/wildduck.ini config/wildduck.ini
@@ -24,6 +28,8 @@ $EDITOR config/wildduck.ini
 
 ### Notes
 
-This is the only delivery plugin you need to use Haraka with WildDuck. Make sure Haraka has no other delivery plugin enabled.
+This is the only delivery plugin you need to use Haraka with WildDuck. Make sure Haraka has no other delivery plugin(s) enabled.
+
+For antispam, WildDuck supports [Haraka's Rspamd plugin](https://www.npmjs.com/package/haraka-plugin-rspamd). WildDuck uses Rspamd output to route messages marked as spam to the Junk mailbox.
 
-For antispam, WildDuck supports Haraka Rspamd plugin. WildDuck uses Rspamd output to route messages marked as spam to the Junk mailbox.
+This plugin includes SPF and DKIM support. You should not enable Haraka's built-in SPF or dkim_verify plugins.