This feature makes it possible for you to assign a "Precedence" value (level of importance) of 0 to 99 to messages. This value signifies the relative sort order of the messages during the delivery process. The lower the value, the higher its importance and the further up it will be in the sort order within a message queue. Thus, MDaemon will attempt to deliver a message with a value of 10 before one with a value of 90. As a guideline for assigning Precedence values: 10 = Urgent, 50 = Normal, and 80 = Bulk.
You will find options related to this feature on the Headers screen under Preferences and on Options screen of the Mailing List Editor. You can also use the Content Filter action, "Add extra header item to message," to insert the Precedence header into any message.