As you might have guessed already, a room is the entity providing this functionality. You need to have at least room-aide privileges to access feature.
Citadel incorporates a fully functional listserver. It provides both single-message and digest modes, and allows self-service subscribe/unsubscribe via Webcit, and Aide controlled subscription. Multiple email addresses can be added at once; You also can choose email addresses from all your addressbooks.
The administration screens in WebCit (Advanced →Advanced room commands → Edit or delete this room → Mailing list service) provide the most intuitive way of configuring and managing a list.
You can do this from the text mode client as well.