Postal continue to supports the Model one (or legacy) configuration format from Postal v2 and before. If you're applying this config file, you can receive a warning within the logs when beginning Postal. We recommend Altering your configuration to Adhere to the new v2 structure which is documented earlier https://postal-smtp-setup66654.ltfblog.com/26423989/apache-support-can-be-fun-for-anyone