A few sites reported that after running the Office 365 1803 update that was pushed with the August patch cycle, Outlook became unresponsive, had longer than normal wait times transitioning in between emails, or continually crashed.
It has been observed that disabling the Symantec Endpoint Protection Outlook Addin in Outlook resolved this issue.
In Outlook browse to File > Options > Addins > Manage: COM Add-ins select Go…
Uncheck Symantec Endpoint Protection Outlook Add in and click OK
