As a newsletter writer who likes to keep his list as clean as possible, I like to remove members who will not read my emails anyway. Blocked trackers and Apple’s Mail Privacy Protection have made it difficult to use open rates as a reliable signal for low interest.
One signal that remains reliable (I believe) is failed delivery. In the detail view of a member, email status distinguishes between sent, opened, and delivery failed.
It would be very helpful if that information were somehow accessible as a filter on all members, as well, allowing me to remove all members who have had, say, 5 failed deliveries in a row.