Applies to: Exchange Server 2013
Topic Last Modified: 2013-02-22
In Microsoft Exchange Server 2013, transport agents that were created using the Microsoft .NET Framework version 4.0 are supported by default. Exchange 2013 supports transport agents that were created using previous versions of the .NET Framework, but support for these legacy transport agents isn't enabled by default. To enable support for legacy transport agents, you need to modify the appropriate XML application configuration file. The files you need to modify depend on where the transport agent is installed:
|Server||Application configuration files||Microsoft Windows service|
Client Access server
Microsoft Exchange Front End Transport (MSExchangeFrontendTransport)
Microsoft Exchange Transport (MSExchangeTransport)
Support for legacy transport agents is controlled by keys in the application configuration files. By default, none of the required keys are present in the application configuration files. You must add the keys manually. The following table explains each key in more detail.
This key enables or disables support for legacy transport
agents. Valid values for this key are
This key specifies the version of the Microsoft .NET Framework that's required by the agent. Valid values for this key are:
You specify multiple values using multiple separate instances of the supportedRuntime version key.
When you enable legacy transport agent support using the
useLegacyV2RuntimeActivationPolicy key, you should always
specify the value
What do you need to know before you begin?
- Estimated time to complete: 15 minutes
- Exchange permissions don't apply to the procedures in this
topic. These procedures are performed in the operating system of
the Exchange Server.
- Changes you save to an application configuration file are
applied after you restart the corresponding service.
- When you restart any of the services that are associated with
the application configuration files, mail flow on the server is
- Any customized per-server settings you make in Exchange XML
application configuration files, for example, web.config files on
Client Access servers or the EdgeTransport.exe.config file on
Mailbox servers, will be overwritten when you install an Exchange
Cumulative Update (CU). Make sure that you save this information so
you can easily re-configure your server after the install. You must
re-configure these settings after you install an Exchange CU.
- For information about keyboard shortcuts that may apply to the
procedures in this topic, see Keyboard Shortcuts in
the Exchange Admin Center.
Use the Command Prompt to configure support for legacy transport agents
Use the following procedure to enable support for legacy transport agents:
- In a Command prompt window, on the Exchange 2013 server where
you want to configure the legacy transport agent support, open the
appropriate application configuration file in Notepad by running
the following command:
- Locate the </configuration> key at the end of the
file, and paste the following keys before the
<startup useLegacyV2RuntimeActivationPolicy="true"> <supportedRuntime version="v4.0" /> <supportedRuntime version="v3.5" /> <supportedRuntime version="v3.0" /> <supportedRuntime version="v2.0" /> </startup>
- When you are finished, save and close the application
- Repeat Steps 1 through 3 to modify the other application
- Restart the associated Windows service by running the following
net stop <service> && net start <service>
net stop MSExchangeTransport && net start MSExchangeTransport
- Repeat Step 5 to restart services associated with the other
modified application configuration files.
How do you know this worked?
You'll know this procedure works if the legacy transport agent installs successfully. If you try to install a legacy transport agent without performing the procedures in this topic, you'll receive an error that's similar to the following:
Mixed mode assembly is built against version '<version>' of the runtime and cannot be loaded in the 4.0 runtime without additional configuration information.