Users report the impossibility of receiving or sending emails through on-premise Exchange 2016 and 2019. It’s all the fault of the automatically installed update of the built-in antivirus.
The message is logged FIPFS 5300
The FIP-FS "Microsoft" Scan Engine failed to load. PID: 24608, Error Code: 0x80004005. Error Description: Can't convert "2201010004" to long.
The only workaround at the moment is to disable the built-in antivirus. To do this, in the Exchange Management Shell, run the following command
& $env:ExchangeInstallPathScriptsDisable-AntimalwareScanning.ps1 -forcerestart