As discussed on the Distribution Lists page, a user can often add himself or herself to a mailing list by subscribing to a Distribution List. If the user has the "Subscribe to Notifications" permission, he or she is allowed to access the Manage > Email Subscriptions page.
This page contains a list of all Distribution Lists that have been marked with the "Open Subscription" flag by an admin user. Any Distribution Lists to which the user has already subscribed himself or herself will be checked; to subscribe to more or fewer of these lists, the user needs only check or uncheck boxes and hit the "Subscribe" button. While a user can subscribe to any unchecked list, he or she can only unsubscribe from any list to which they subscribed personally. If an admin user adds a user to a Distribution List, that user cannot override that decision and unsubscribe from that list; lists to which a user has been added by an admin will appear on the page as checked, but are grayed out and cannot be unchecked.
Any users that have subscribed themselves to a Distribution List will appear as recipients of that list like any other on the Distribution Lists page. As a result, an admin user can remove a self-subscribed user from the Distribution List, though as long as the list is still flagged as "Open Subscription", that user can simply re-subscribe to the list. An admin user can, however, remove the "Open Subscription" flag from a Distribution List even after users have subscribed to it, which will prevent normal users from adding or removing themselves from lists, but will not remove them as recipients of those Distribution Lists; in essence, those subscriptions are frozen as is, but admin users can continue to add or remove users. If the "Open Subscription" flag is once again given to that Distribution List, users will once again be able to add themselves to that list, or remove themselves if they originally subscribed to it themselves.
To the right of the list of all open Distribution Lists lies the Subscriptions block. This block shows a summary of what events will trigger a notification to be sent to each checked Distribution List. To recap, notifications can be sent in response to either System Events or Service Events. System Events are triggered automatically by the system in response to certain predefined events, but Service Events are user-defined and are only triggered by routines. So, the Subscriptions block shows every System Event of which the user will be notified, and which Distribution Lists are notified in response to each; additionally, it lists the origin events of all rules that can trigger a Service Event that notifies a checked list, such as a form submission, device message, etc., as well as which Service Events are triggered, and which Distribution Lists those Service Events notify.