Priority Queue – Let the Important Mails Flow !



A pretty big agency who was the front runner for a major deal with a retail organiation almost lost a major deal due to delayed delviery of the proposal. The proposal email did go out, but a bit too late to be considered. The Account Manager complained against the IT Staff to the Top Management. So who was the fall guy – our obvious IT GUY (as they call him / who happens to be my friend too). The top management ignored that Account Manager delayed sending out such an important email that too at the fag end of a financial quarter ending, when mailflow is on the higher side, resulting in long mail queues.

This IT GUY was blamed for the badly managed Exchange environment that according to the management was the reason for such an issue, though he had been fighting with the management on increasing the bandwidth due to over utlization – but did any care to listen? So….. This friend came to me and asked what needs to be done? Well, Enable & Configure Priority Queuing !!

Priority Queuing

In Exchange Server, Priority Queuing helps processing of a message that has been defined as High Priority by user (via Microsoft Outlook, refer X-Priority header field in Message Header) before the other messages in the queue. Basically, messages that are for same destination (like External) are put in the same delivery queue and when priority queuing is enabled, High priority messages are transmitted first, then Normal messages and finally the Low priority messages.

  • Enable Priority Queue:
    • Go to C:\Program Files\Microsoft\Exchange Server\Bin directory and open the EdgeTransport.exe.config file. Set the PriorityQueuingEnable parameter value to True
    • Restart the Microsoft Exchange Transport service.
  • Configuration for High Priority Message
    • Configure Maximum Size of High Priority Message It is imperative that the maximum size of High Priority Messages is kept on the lower side (default for normal messages is 10 MB) depending upon organizational needs Go to C:\Program Files\Microsoft\Exchange Server\Bin directory and open the EdgeTransport.exe.config file. The defauly value of MaxHighPriorityMessageSize parameter value is 250 kilobytes (KB). Note: Any larger message is automatically downgraded from High priority to Normal priority. For Exchange 2007 SP1, refer to
    • Configure Delay Notification The delivery status notification (DSN) message for delayed messages is sent only after a specified delay notification time-out interval, and only if the failed message wasn’t successfully delivered during that time. The default time for High Priority Messages is 30 minutes.
    • Configure Message Expiration Time-Out Once the DSN has been sent, the Hub Transport server tries to deliver a message for a period of time. The message expiration time-out specifies the maximum length of time the message is tried and for High Priority Messages is 8 hours. Note: Based upon the organization needs it should ideally be reduced.

Tackling Troublesome Users:

Well, another question that cropped up was that once we enable Priority Queuing, then there will be users who will always send Messages as High Priority. Well, yes this is pretty normal, but then in such cases it is ideal to identify those users and configure their mailboxes to downgrade all their high messages to normal

Configure the DowngradeHighPriorityMessagesEnabled parameter using the Set-Mailbox to achieve the same. The default value is False. When this parameter is set to True, any High priority messages sent from mailbox are automatically downgraded to Normal priority.

So, Let the Important (High Priority) Mails Flow 🙂 !