NOTE: The problem discussed in this article was fixed in Exchange 2013 Cumulative Update 5. To avoid the problem altogether we can skip SP1 (aka CU4) and go for CU5 directly.
Now that Exchange 2013 Service Pack 1 has been available for a couple of weeks, the Exchange community is taking stock of the progress made in various areas. SP1 is an important milestone, it is the green flag that many await before moving to a new Exchange version.
As always it is impossible for a release to be perfect and some problems have already been identified. Here I document a problem everyone should be aware of. This can take down the Exchange Transport service, stalling the email flow. Otherwise it can leave an installation without critical functionality provided by 3rd party Exchange add-ons.
Luckily Microsoft promptly provided a fix and it is easy to apply. So my goal here is to increase the awareness so that no one is caught by surprise.
The problem concerns the Exchange Transport Agent interface. It effects most on-premises email hygiene solutions as well as other applications tapping to the mail flow through this interface.
Problem Description
The problem can take two twists depending on the order of how things are installed.
Scenario 1 - Exchange 2013 SP1 is successfully installed and working fine. We then try to install a product that includes an agent built to run with pre-SP1 Exchange 2013. The agent installation will fail. Of course the error reported by the installation will be application specific.
The 3rd party application installation will typically either fail to install altogether, or it might install without the agents. Either way the application won't be able to tap into the email transport and won't function as intended.
Scenario 2 - We start from a pre-SP1 Exchange 2013 installation where a 3rd party transport agent is already installed and working fine. We then upgrade to Service Pack 1. In this case Exchange 2013 SP1 finds an agent that it is unable to load. The Microsoft Transport service fails to start and the email flow is stuck.
If we look at the Application event log here we find event log errors:
Source: MSExchangeTransport, Error: 16023
Source: MSExchange Extensibility, Error: 1052
The errors will point at the 3rd party agent and will be on the lines:
"Microsoft Exchange couldn't start transport agents. The Microsoft Exchange Transport service will be stopped. Exception details: Failed to create type..."
Fixing Exchange 2013 SP1
Microsoft was quick to release a script that fixes this issue. Here is it:
KB2938053 - Third-party transport agents cannot be loaded correctly in Exchange Server 2013
Before installing the fix it is helpful for us to clearly understand which of the two scenarios are we dealing with.
The best case scenario is the one where we have a fresh Exchange 2013 SP1 installation. Apply the fix immediately before installing any 3rd party application. I recommend installing this fix even if there are no short term plans to install 3rd party applications. Technically the fix is just a simple script which corrects some redirections that should always be there. If the fix is applied straight away we avoid having to remember of this article.
If we discover the problem after attempting to install a 3rd party application, then most likely the solution is to apply the Microsoft fix and to re-install the 3rd party application. Note that here I am still looking at scenario 1.
In case of scenario 2, the most likely solution is to apply the Microsoft fix and to manually start the Microsoft Exchange Transport service from the Service Control Manager. This will allow the transport to correctly load the pre-SP1 agent and bring the email transport back to life.
Applying KB2938053 Fix
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Follow the link:
Third-party transport agents cannot be loaded correctly in Exchange Server 2013
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Click the Fix it button.
At the Download box click Open to download and run the fix.
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The Microsoft Fix It Solution wizard starts
Click Next to start running the fix.
Click Next and Close to complete the Wizard.
Final Tips
Today we looked at the Exchange 2013 SP1 transport problem with 3rd party agents. Here I tried to give a generic explanation of what is going on without getting into the specifics of any product. My advice is obviously for you to check with your software vendor. With time, applications may incorporate the Microsoft fix in their own software or provide other workarounds.
References
Third-party transport agents cannot be loaded correctly in Exchange Server 2013