For an issue that is not solved by disabling the feature, but is solved by disabling the add-in, then there is no easy workaround.
Either the add-in must be disabled, or the email-scan feature removed (which can only be done via ePO by uninstalling and reinstalling with the command line setting to not install the EmailScan feature - see the Install Guide for command line info)
To investigate the crash so it can be root caused, and if our code is responsible - addressed - then you'll want to capture crash dump information of the failure, and provide the dump to Support.
William W. Warren | S.I.R.R. | Customer Success Group | McAfee