This exception code (0xe0434352) is unfortunately not very indicative of the root cause so we'll likely need to check some additional logs with you. If you do a quick search of the logging on your server do you find any repeating errors being logged in any particular log file? 

I typically start my review in the Error logging and then move to protocols like IMAP/MAPI/etc. If you find a repeated error you can usually see which user is triggering it as well and that should give you a path to begin troubleshooting on. 

Douglas, we'll get a ticket started with you on this. Thanks for reporting it.