list key differences between config files

content/2.getting-started/4.configuration.md

@@ -26,3 +26,18 @@ You can use the `PORT` and `BIND_ADDRESS` environment variables to provide insta
 The current version for the Postal configuration file is `2`. This is shown by the `version: 2` in the configuration file itself.
 
 Postal still supports the version 1 (or legacy) configuration format from Postal v2 and earlier. If you are using this config file, you will receive a warning in the logs when starting Postal. We recommend changing your configuration to follow the new v2 format which is documented above.
+
+The key differences between v1 and v2 configuration is shown below.
+
+* `web.host` changes to `postal.web_hostname`
+* `web.protocol` changes to `postal.web_protocol`
+* `web_server.port` changes to `web_server.default_port`
+* `web_server.bind_address` changes to `web_server.default_bind_address`
+* `smtp_server.port` changes to `smtp_server.default_port`
+* `smtp_server.bind_address` changes to `smtp_server.default_bind_address`
+* `dns.return_path` changes to `dns.return_path_domain`
+* `dns.smtp_server_hostname` changes to `postal.smtp_hostname`
+* `general.use_ip_pools` changes to `postal.use_ip_pools`
+* `general.*` changes to various new names under the `postal.` namespace
+* `smtp_relays` changes to `postal.smtp_relays` and now uses an array of strings which should be in the format of `smtp://{host}:{port}?ssl_mode={mode}`
+* `logging.graylog.*` changes to `gelf.*`