Written
September 15, 2015
When we attempt to install the agent on Exchange 2013 we receive the following error:
[PS] C:\Windows\system32>Install-TransportAgent -Name ShowDLInSubjectAgent -TransportAgentFactory ShowDLInSubjectAgent.ShowDLInSubjectFactory -AssemblyPath C:\TransportAgents\ShowDLInSubjectAgent.dll
Could not load file or assembly 'file:///C:\TransportAgents\ShowDLInSubjectAgent.dll' or one of its dependencies.
Operation is not supported. (Exception from HRESULT: 0x80131515)
+ CategoryInfo : InvalidArgument: (:) [Install-TransportAgent], FileLoadException
+ FullyQualifiedErrorId : [Server=mailbox,RequestId=1c74a8e1-adae-46ac-a5f05a70a2572dfe,TimeStamp=9/15/2015 10:41:12 PM] [FailureCategory=Cmdlet-FileLoadException] DB2F4840,Microsoft.Exchange.Management.AgentTasks.InstallTransportAgent
+ PSComputerName : mailbox.domain.com
We unblocked the DLL as some have suggested without any change. We also enabled legacy agents by editing the EdgeTransport.exe.config and MSExchangeTransport.exe.config files as described here: https://technet.microsoft.com/en-us/library/JJ591524(v=EXCHG.150).aspx