Message Storage

A messaging application receives a sequence of user-consumable messages directed to at least one destination user. The messages are stored in non-volatile storage comprising one or more non-volatile storage devices, and the messages consist of a number of consumed messages having been consumed by the destination user, and a number of unconsumed messages not yet having been consumed by the user. An automatic message manager is configured to implement different respective retention policies for the consumed messages and the unconsumed messages. The retention policy for the consumed messages comprises automatically determining when the number of consumed messages exceeds a threshold for consumed messages, and in response automatically deleting at least one of the consumed messages from the non-volatile storage so as to bring the number of consumed messages back within the threshold for consumed messages.