ezmlm automatically handles bounces in a manner that assures that subscribers are not removed due to temporary failures, but at the same time removes addresses that fail continuously (for more than 3 weeks).
ezmlm uses VERP. This way, ezmlm knows the subscriber address corresponding to any bounce received. ezmlm keeps track of bounces and after about 11 days sends a list of missed messages to the subscriber.
If this message bounces, ezmlm waits another 11 days, then sends a probe message to the subscriber. If this probe message bounces, the subscriber address is removed.