For message delivery in a communication network, message processing is monitored, including processing of a first message by subscribers of a network application that provides messaging services via the communication network. A group activity level is determined for processing of the first message by ones of the subscribers who belong to a first group of persons. The determined group activity level is compared to a threshold activity level for the group. Responsive to the determined group activity level exceeding the threshold activity level, a notification about the message is sent via the communication network for a subscriber who belongs to the first group and has not processed the first message.