A Distribution List is a list of email addresses and/or account users that can serve as the recipient of an email notification. There can be overlap between the desired recipients of notifications for different System or Service Events; for example, a user may want to inform every administrator of a facility when a Service Event titled "Possible Break-In" is triggered, as well as for a "Critical Machine Failure" event. The user could create an email notification for each of these Event Types and manually list out every administrator, but this is time-consuming and creates more room for mistakes. Instead, the user could create a single Distribution List called "Admin", add all administrators to this list, and set the recipient of each notification to the Distribution List. The use of a Distribution List also simplifies the process of changing which people are notified in response to events. If a new administrator is hired, rather than add that person to each email notification manually, a user can simply add the new administrator to the "Admin" list, and he or she would immediately begin receiving all relevant notifications.
Distribution Lists can also include other Distribution Lists as Recipients, called Sub-Lists. After all, if a user wishes to create a Distribution List containing users of type A and type B, and lists already exist of each type individually, it is much easier to add the latter as sub-lists than to manually add every user of type A or B to the new list. This would also allow a change in the Distribution List of type A to automatically be reflected in the parent list, in the event that, for example, a type A user quits. Any Distribution List can be added as a sub-list to any other list, unless doing so would create a loop in which a Distribution List is its own sub-list, either directly or indirectly. For instance, if list A includes list B as a sub-list, and list B contains list C, then list C would be unable to add list A as a sub-list.
Typically, recipients are added to a Distribution List by an admin user with the permissions necessary to access the Distribution List page. The "Add Contact", "Add User" and "Include Sub-List" buttons allow an admin user to add as a recipient a raw email address, account user, or other Distribution List, respectively. However, an admin user can also check the "Open Subscription" flag of a Distribution List, allowing any non-admin user with the necessary permissions to subscribe himself or herself to a list. Self-subscription is covered in more detail on the next page, Subscriptions.