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What types of Exchange transport queues are there?



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 as of PRTG 22

Types of transport queues in Microsoft Exchange

PRTG comes with two sensors for monitoring Exchange queues:

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 systems the messages are queued:

  • The Edge Transport role for messages coming from and going to the internet.
  • 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 QueueMessages that must be resolved, routed, and processed by transport agents.
Mailbox Delivery QueueMessages that are delivered to a mailbox server via encrypted Exchange RPC.
Remote Delivery QueueMessages that are delivered to a remote server via SMTP.
Poison Message QueueIsolated messages that are considered to be harmful to the Exchange system after a server failure and that are typically empty. Messages in this queue are suspended by default.
Unreachable QueueMessages that cannot be routed to their destinations.

The Exchange Mail Queue (PowerShell) sensor shows the additional channel Retrying Mails. This channel shows messages that could not be successfully delivered but make connection attempts with the destination domain.


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

Last change on Jan 3, 2023 9:31:42 AM by  Brandy Greger [Paessler Support]

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