Each queue has a suffix of Ppriority number, where P1 is the highest priority. The message queues are treated as FIFO (First In, First Out), and new messages are always added to the end of the queue.

The Exchange Public Folder task will process the queues in order of priority. The task scans through each queue, starting with the highest priority. If it finds a message on a queue, it will process the message, and then start the scan again from the highest priority queue. Therefore, if there are messages on queue P1, the other queues will not be processed until queue P1 is empty.

However, the P5 queue is a special queue only used during the public folder archiving schedule. The Exchange Public Folder task will process only messages on queue P5 during a scheduled archive period. Outside of the schedule, any messages on these queues will be ignored.

Queue P3 performs the same function as queue P5, but for an administrator Run Now. This queue also performs shortcut expiry and deletion.

Queue P5 will only be processed during a scheduled period, but queues P1 and P3 will always be processed. If a queue has not been processed for more than 10 minutes, and there are no messages in a higher priority queue, there may be a problem with the task. Check the Enterprise Vault event log on the Exchange Public Folder task computer for any additional information.

Monitoring queue P1 will indicate that a backup has correctly updated shortcuts. However, if P1 is being used during normal use (before a backup), it may indicate a problem with tasks. Check the Enterprise Vault event log for errors.