[KB3026] Microsoft Transport Agent service will not start after removing ESET Mail Security for Exchange

• After uninstalling ESET Mail Security for Exchange using the ESET uninstaller utility, the Microsoft Exchange Transport Agent does not start, and one or both of the following have been added to the Application Event Log:
  
  Log Name: Application                                                               Log Name: Application
  Source: MSExchange Extensibility                                           Source: MSExchange Extensibility
  Date: x/xx/xxxx x:xx:xx AM                                                              Date: x/xx/xxxx x:xx:xx AM          
  Event ID: 1052                                                                              Event ID: 16023
  Task Category: MExRuntime                                                     Task Category: Configuration
  Level: Error                                                                                    Level: Error 
  Keywords: Classic                                                                       Keywords: Classic
  User: N/A                                                                                       User: N/A
  Computer: server.FQDN.local                                                   Computer: server.FQDN.local

There are two solutions to resolve this issue. Start with solution 1 and only continue to solution 2 if the issue is unresolved.

Solution 1: Remove ESET Filtering Agents using the Exchange management shell

1. Open the Exchange management shell.
    
2. Type the command Get-TransportAgent and press Enter.

3. Find and make note of the two ESET Transport Agents:

   • ESET Filtering Agent 
   • ESET Filtering AV Agent 

4. In the Exchange management shell, type Uninstall-TransportAgent and press Enter.
   
   
5. You will be prompted for the identity of the agent to uninstall. Type ESET Filtering Agent, then enter Y and press Enter.

6.  In the Exchange management shell, type Uninstall-TransportAgent.

7. You will be prompted for the identity of the agent to uninstall. Type ESET Filtering AV Agent, enter Y and press Enter to confirm.

8. After successfully removing the two filtering agents, open a run command (Windows key + R) and enter "services.msc". Locate the MSExchange Transport service and restart it, or start it if it is not already running.
    
9. The transport agent should now start and run as normal. Monitor the service in the event log, or the services snap-in to ensure it does not stop again. If the transport agent still does not start, continue to solution 2.

Solution 2: Manually edit the agent.config file

1. Browse to %Program Files%\Microsoft\Exchange Server\V14\transportRoles\shared\, then right-click the file named agent.config and click Open with → Notepad from the context menu.
    
2. Locate the "agent name=" entries for ESET Filtering Agent and ESET Filtering AV Agent and delete those lines from the file.

3. Save the file, open a run command (Windows key + R) and enter "services.msc". Locate the MSExchange Transport service and restart it, or start it if it is not already running.
   
   
4. The transport agent should now start and run as normal. Monitor the service in the event log or the service snap-in to ensure it does not stop running again.