After installing SP1 for Microsoft Exchange 2013, you can expect some issues.
One of them is that after applying SP1 your Exchange server will stop accepting inbound emails and connections to port 25.
If you check Event Log, in Applications Log you will find entries with ID 7012 with source MSExchangeFrontEndTransport and with information:
“The service state for frontedn transport is inconsistent. Current state – Inactive. Expected state – Active.”
Using Powershell you can check state of this component:
Get-ServerComponentState servername01 -Component FrontendTransport
But you will see that this component is Active.
Also you can test inbound external email using Microsoft Remove Connectivity Analyzer, where you can find information about connection error to TCP port 25.
To resolve this issue you need to restart Microsoft Exchange Frontend Transport service.
You can do this using Powershell:
or just restart service in Services.msc.
When you do this, your server should now accept connections to port 25, and also you shouldn’t see warnings in Application Log.