Exchange Server 2013 SP1 breaks installing third party transport agents

Problem

Following successful installation of the Email Signature Manager Transport Agent on Exchange Server 2013 SP1, the transport agent has not actually been installed.

When executing the Get-TransportAgent cmdlet in the Exchange Management Shell, the Email Signature Manager Transport Agent is not listed.

When attempting to manually install by executing the Install-TransportAgent cmdlet an error occurs about the TransportAgentFactory type being incorrect.

Reason

This is a known issue with Exchange Server 2013 SP1. The global assembly cache (GAC) policy configuration files contain invalid XML code.

Solution

Follow these steps to resolve the problem:

1. Uninstall the Email Signature Manager Transport Agent.
2. Install Exchange Server 2013 Cumulative Update 5 (CU5) or newer.
3. Reinstall the Email Signature Manager Transport Agent.

Applies to

Email Signature Manager, version 8 and later