address_metrics_cleanse_interval — the interval for refreshing address metrics
address_metrics_cleanse_interval = 3600
Address metrics store data on the quality of service to a particular target host from a particular binding; data such as the time since the last failure, and how long it takes to connect and to deliver a message. Address metrics are used to determine which of a domain's MXs to open more connections to.
address_metrics_cleanse_interval controls how often stale entries are cleaned up. Normally this option does not need to be changed.
The default value is 3600 seconds.
address_metrics_cleanse_interval is valid in the global scope.