KB ID 0001447
If your Exchange 2010 Server Stops working after a 6 to 12 hour window, then this is a known problem caused by last months (July 2018) security updates. You will also notice that the ‘transport service‘ becomes unresponsive.
Note: A reboot will temporarily fix the problem but the server then ceases to function after the same time.
Which update you need to uninstall, depends on your operating system (2008/2012)
Server 2008 R2
KB4338423 and KB4338823
Server 2012 R2
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