I performed a back up of Exchange 2013 on a 2012 R2 server using Windows Backup and after completion, on premise Outlook users could not connect to the server. I can connect via OWA and active sync but cannot send or receive email. It appears mail is sent as nothing in the outbox but external recipients are not receiving.
Mail store is connected and all automatic Exchange services all running. All inbound and outbound connector are enabled. Nothing in the event logs point to any issues.