There may only be one of these lines. The job creation time. This is used to compute when to time out the job. The current message priority. This is used to order the queue.
Higher numbers mean lower priorities.
The priority changes as the message sits in the queue. The initial priority depends on the message class and the size of the message. M A message. This line is printed by the mailq command, and is generally used to store status information. It can contain any text.