Available Delivery Modes
The entry in this field indicates the delivery methods available for messages posted to this list. Possible options are: Immediate Only, Digest Only, and Digest or Immediate. The Immediate mode of delivery sends you messages as soon as they are posted to the list. The Digest mode holds posted messages so that they can be delivered to you in a group on a regularly scheduled basis (see the Digest Schedule entry to determine when group delivery will occur).
When subscribing to a list you should consult this field first to determine which delivery modes are