After you install Microsoft Exchange Server 2013 Service Pack 1 (SP1) or you upgrade an existing Microsoft Exchange Server 2013 installation to Exchange Server 2013 SP1, third-party or custom-developed transport agents cannot be installed correctly.
Additionally, the Microsoft Exchange Transport service (MSExchangeTransport.exe) cannot start automatically. Specifically, you cannot enable third-party products that rely on transport agents. For example, you cannot enable anti-malware software or custom-developed transport agents.
Products experiencing the issue are:
- TrendMicro ScanMail
- McAfee Email Security (GroupShield)
- Symantec Mail Security for Exchange
- AVG for Servers
- ESET Mail Security for Exchange
- CodeTwo Exchange Rules
This problem occurs because the global assembly cache (GAC) policy configuration files contain invalid XML code.