Spent the last 5 hours uninstalling SmarterMail, rebooting, reinstalling SmarterMail, rinse & repeat to no avail. Upgraded from v16.3.6821 Enterprise edition to v16.3.6841 but the web-interface would not load in any known major browser (Chrome, Firefox, Edge, IE11, Vivaldi, Safari, Opera, Brave, etc.). Did the CTRL+F5, tried Private/Incognito tabs, tried clearing browser cache, etc. (even tried clean new browsers on a brand new OS in VirtualBox) but nothing would coax SmarterMail into loading other than uninstalling v16.3.6841 and rolling back to v16.3.6821...after which the web-interface loaded immediately without issue or jumping through any hoops on the first attempt in every browser.
Note: Interestingly localhost could display the web-interface but for everyone else there was nothing but a blank screen.
We are running on Windows Server 2016 if that matters.
I'm giving up. This is the second time in less than a month that this has happened with an update. Sadly we just renewed our license with SmarterMail this month, otherwise we'd be gone (just like all of our customers who tired of this over the course of the past 17 months).