Using Classic Outlook on Windows for personal email, calendar, and contact management
I have clients also reporting this issue. We put them all on current channel and updated them. Of the people in our office only 4 have reported the issue and all are on Windows 8.1, using Office2016, Office365 Enterprise E3 license types.
In our case the characteristic is two FULL Internet Explorer windows open on the close of Outlook. Most of the time the windows open with no error and just open to the IE home page that is set.
I am writing this off to our client as a known issue/bug with a recent office update and awaiting resolution from Microsoft Support.
I hope this information helps in the quest to push a resolution.
-SaraS