After upgrading to Symantec Mail Security (SMSMSE) 7.5 it is noticed that the Exchange Transport service can not start and mails can not be delivered.
Microsoft Exchange couldn't start transport agents. The Microsoft Exchange Transport service will be stopped. Exception details: Failed to create type 'Symantec.MailSecurity.Server.TransportAgent.SMSMSESMTPAgentFactory' from assembly 'D:\Program Files\Symantec\SMSMSE\6.0\Server\Symantec.MailSecurity.Server.TransportAgent.dll' due to error 'Invalid agent assembly path.'. :
It is not supported to upgrade to SMSMSE 7.5 from SMSMSE 6.0. Exchange transport service is depended on all agents being able to start up. Since during upgrade the SMSMSE agents can not be properly uninstalled Exchange transport service is trying to load the old SMSMSE transport agents which will fail. After the agents fail to start up the Exchange transport service will also fail to start up as per error message above.
Perform the following
1. Uninstall SMSMSE 7.5 from Programs&Features. Ensure the uninstallation is successfull.
2. Go to the SMSMSE installation path and move away the SMSMSE and CMaF folders.
3. In Exchange Management Shell ensure the SMSMSE transport agents have been uninstalled with command: get-transportagent
4. Install SMSMSE 7.5. Ensure the installation is successfull.
5. Check in services.msc that both "Microsoft Exchange Transport" service and "Symantec Mail Security for Microsoft Exchange" is started.
If both services are started and continously running the problem should be resolved.
Windows 2008 server
Exchange 2007 or Exchange 2010
Symantec Mail Security 7.5