JIRA administrator can configure the global settings of Email Notifications Digest for all users in the system.
Global configuration allows to turn on/off the digest for all users, define the maximum amount of updates per digest and default email digest schedule.
Global Email Notification Digest Configuration is available from JIRA Administration → Add-ons → Manage Add-ons → Email Notification Digest add-on → Configure button.
Alternatively, global configuration can be opened from a personal configuration page (if user has JIRA Administrator permission).