MSExchangeTransport Queues(_total)Retry Remote Delivery Queue Length
-Shows the number of messages in a retry state in the remote delivery queues.
-Shouldn’t exceed 100. We recommend that you check the next hop to determine the causes for queuing.
In my daily monitoring of our Exchange 2010 servers, I glance at the Exchange Server Performance Monitor on both our CAS/HUB server, and the MBX server. This allows me to see any abnormal activity pretty easily with lines on a graph. If there are high spikes, or sustained heightened activity, I will usually investigate. Since ive been working with Exchange I have noticed there are always a substantial amount of messages stuck in the Retry Remote Delivery Queue Length. When I go into Queue Viewer and click the messages tab, I can view all of the messages that are causing the large queue size. Normally this is between 30 and 100 messages. These messages are addressed to recipients that do not exist in our organization with the error 400 4.4.7 Message Delayed, and keep retrying.
So what is causing these queued messages?