Retained message and message expiration interval of EMQX MQTT 5.0 brokerThe message retention function of [EMQX MQTT Broker](https://emqx.io) is implemented by the `emqx_retainer` plugin, which is enabled by default. By modifying the configuration of the` emqx_retainer` plugin, you can adjust the EMQX Broker's retention message Location, restrict the number of retained messages and maximum payload length, and adjust the expiration time of retained messages.
