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What types of Exchange transport queues are there?



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I can monitor mail and transport queues of Microsoft Exchange servers with several native sensors of PRTG. What are the different kinds of Exchange transport queues and what are they used for?

exchange exchange-powershell exchange-queue mail-queue message-queue microsoft prtg queue transport-queue

Created on Jul 12, 2013 9:42:20 AM by  Gerald Schoch [Paessler Support]

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This article applies to PRTG Network Monitor 19 or later

Types of transport queues in Microsoft Exchange

There are two types of out-of-the-box sensors for monitoring Exchange queues: the Exchange Mail Queue (PowerShell) sensor and the WMI Exchange Transport Queue sensor. Both can monitor various values of an Exchange queue, such as the length of specific queues.

A queue can be defined as “a temporary holding location for messages that are waiting to enter the next step of processing”, or as the "number of messages with the same status". Different server roles determine on which computers the messages are queued:

  • The Edge Transport role for messages coming from and going to the internet, and
  • The Hub Transport role for messages within the Exchange organization.

The routing of a message determines the type of queue in which a message is stored. In Exchange, there are five types of queues with different kinds of messages:

  • Submission Queue: Messages that have to be resolved, routed, and processed by transport agents.
  • Mailbox Delivery Queue: Messages that are delivered to a mailbox server by using encrypted Exchange RPC.
  • Remote Delivery Queue: Messages that are delivered to a remote server via SMTP.
  • Poison Message Queue: Isolated messages that are considered to be harmful to the Exchange system after a server failure; typically empty; messages in this queue are suspended by default.
  • Unreachable Queue: Messages that cannot be routed to their destinations.

The Exchange Mail Queue (PowerShell) sensor shows the additional channel Retrying Mails. This channel sums up the messages that cannot be successfully delivered but have a renewed connection attempt with the destination domain.

For more information regarding transport queues, queue database files, or options for configuring and management, refer to the Microsoft TechNet article Understanding Transport Queues.

Created on Jul 12, 2013 9:46:19 AM by  Gerald Schoch [Paessler Support]

Last change on Dec 10, 2020 9:34:47 AM by  Brandy Greger [Paessler Support]

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