Cause: The default postfix configuration uses `inet_interfaces = localhost` which tells postfix to listen on all interfaces resolving to `localhost` including both IPv4 and IPv6 interfaces. Consequence: If IPv6 is disabled on the host, postfix and command line tools such as postconf will issue an error, and the role will fail. Fix: Using `postconf -h default_database_type`, see if postconf fails with the error message that indicates IPv6 is disabled. If so, then set `inet_protocols = ipv4` so that postfix will only use the IPv4 interface. Result: The postfix role works when IPv6 is disabled. Adds a new test tests_disable_ipv6.yml to check for this. Signed-off-by: Rich Megginson < rmeggins@redhat.com > ## Summary by Sourcery Detect IPv6-disabled environments and configure postfix to use only IPv4, streamline configuration management, and add an integration test for IPv6-disabled hosts. New Features: - Auto-detect when IPv6 is disabled and set postfix to listen only on IPv4 - Add a test playbook to validate the postfix role on an IPv6-disabled host Enhancements: - Consolidate configuration application by delegating to manage_config.yml Tests: - Introduce tests_disable_ipv6.yml to verify role behavior with IPv6 disabled