Relay tasks produce user notifications. By default, each notification creates an email for each user who has access to the task. This is suitable in a single-user Relay environment, but can get overwhelming in a multi-user Relay environment with a lot of activity.
The notification manager manages this by applying rules to the notifications. The notification manager can build complex rules which route different types of messages to different users, or add, remove and change recipients. However, the commonest use case is to batch up most notifications into a smaller number of emails, with exceptions for some higher priority notifications.
The notification manager is installed into an account and connected into the portal, in a similar way to Relay. It intercepts outgoing notifications and manages them according to rules. The rules are maintained within the portal.
Notification manager - technical reference provides technical details.
The notification manager does not modify non-task emails, such as connection request emails and forgotten passwords emails, and other mechanisms are available to modify those emails.