This plugin checks if any sender has exceeded a rate limit as defined in

This plugin checks for senders that exceeded a sending limit and returns a critical error if anyone reached his limit thus making it possible to react fast to a spaming account. A valid postfwd installation and configuration is required. Simply invoke it with the rate limits that should be verified:

    ./check_postfwd_rate -l 500,1000

It may take some time until the cache gets filled up by postfwd upon restarting the postfwd service.