There are three types of notifications: immediate, scheduled and optional scheduled.
Immediate notifications
Immediate notifications are mandatory for activities that requires immediate attention. These are sent as emails to users who are directly involved in the activities. For example:
Project manager changes
Project field updates
Project sharing
Work and subtask status changes
Work and subtask assignee changes
Work and subtask updates
Comments with direct (@) mentions
Budget threshold reached
Approval requests and confirmations
User invitations and role changes
Scheduled notifications
Scheduled notifications are also mandatory, for activities that requires periodic attention. These are sent as emails to users who are directly involved in the activities. For example:
Work start and due reminders
Pending invitation reminders
Optional scheduled
Optional scheduled notifications can be scheduled by users for Never, Daily or Weekly in Personal Settings. These include:
Project summary
Portfolio summary
All scheduled notifications are sent between 1:00 am PST and 3:00 PST.