Why does Outlook launch IE in the background?

That's the Microsoft Store version of Office, which is not updated at the same frequency as Click-To-Run. You can uninstall that and go to office.com and install the Click-To-Run version.

That's the Microsoft Store version of Office, which is not updated at the same frequency as Click-To-Run. You can uninstall that and go to office.com and install the Click-To-Run version.

1.  How do I uninstall the store version (Win10).  It's not in CP\ProgsAndFeatures.  [And can I rid Win10 of all traces of the store?]

2.  When I go to office.com, I eventually wind up at account.microsoft.com where my install choices are six:  32 & 64, Insider 32 & 64, Monthly Targeted 32 & 64.

Which do I want?

In spite of the additional officeclicktorun.exe process.exe, I prefer the click-to-run install.  It has less file system smoke and mirrors, and commands like "excel" work at command prompts and in start/run.

It's called "Microsoft Office Desktop Apps" in Apps & features.

Read this: https://docs.microsoft.com/en-us/DeployOffice/overview-of-update-channels-for-office-365-proplus to understand which channel you want to choose. The build for *this* issue will show in Insider first, then Monthly, then Targeted.

32 bit vs 64 bit depends on whether you have any older com-addins you need to run. If you do, you likely need 32 bit for compatibility. Otherwise 64 bit should be your default choice.

Thanks for all your help, Stephen.  Nothing on the Win10 machine is old.  Outlook has an "Exchange" COM add-in (UmOutlookAddin.dll).  I connect to exchange.  I have the 32-bit version now (recommended by the store) but would prefer 64-bit.   ???

We just checked in a fix to build 16.0.11005.37379, so any Insider Fast build higher than that should have the fix.

I just checked on the integration status. Integration happened in build 16.0.11012.10000. So that's the build to really watch for.

We have also noticed this behavior and are testing with the Monthly-Targeted channel (build: 16.0.11029.20045).  We have IE Protected Mode turned on for Internet Zone and Restricted zone, but off for Intranet and Trusted Sites.  We have tested turning it on for trusted sites and Intranet zones but are still experiencing the same symptoms (When launching Outlook in Safe Mode or otherwise, 3 IE processes are launched.  When closing Outlook 2 IE processes remain).  I have also verified the registry key (HKCU:\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\ProtocolDefaults\osf-roaming.16=3)

Are there other Office or Internet Explorer settings that could interfere with the implemented fix?

If it is helpful, I can open a premier case so we can do some screen sharing as well.

Thanks!