I came in to work on Monday with a rather large client with no email. They run Microsoft Exchange 2007. I first logged in to the server and owa to ensure the Exchange Server was actually functioning. All services were going.
I then opened the message queue. There I saw 350 emails with the Last Error set to message deferred by categorizer agent
I haven’t actually come across this error before. Something had changed on the system. To cut a long story short, I found the issue was because of a corrupt transport agent. To find your transport agents, run the following power shell command:
You will get a list like the following
Identity Enabled Priority
-------- ------- --------
Transport Rule Agent True 1
Journaling Agent True 2
AD RMS Prelicensing Agent False 3
Connection Filtering Agent True 4
Content Filter Agent True 5
Sender Id Agent True 6
Sender Filter Agent True 7
Recipient Filter Agent True 8
Protocol Analysis Agent True 9
In the event log, I noticed the following error
An error occurred while loading the configuration for the Journaling agent. The configuration may be corrupt, or the Active Directory directory service may be down or unreachable. The last known good configuration will be used, and the Journaling agent will attempt to read the configuration again later.
This restored configuration didn’t fix the issue. I opted to disable the Journaling Agent.
Disable-TransportAgent -Identity "Journaling Agent"
Select Y and then restart the Hub Transport service.
This should fix your issue. I am still investigating a fix for the Journaling Agent. I suspect this was initially caused by a reboot when performing Windows Updates as the mail flow stopped on the same day.