Why does Outlook launch IE in the background?

I did say why - I explained the whole thing on May 10th.

I never shut down Outlook.  So two instances of iexplore.exe are SUPPOSED to be running as long as outlook.exe is running?  No one has said WHY!  It sounds bogus to me.  There's no guarantee that Internet Explorer will even be among the "turned on" Windows features. 

In fact, turning off the "Internet Explorer 11" feature certainly keeps Outlook from starting it.  That's just what I did.  Outlook doesn't seem to mind a bit.  And I doubt I'll miss IE.

We're seeing that here as well (I reprod on 16.0.10815.20000). It doesn't appear to repro if protected mode is set to the defaults. Dev is investigating.

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

Level setting: Outlook is expected to open IE when it starts. That is by design. The bugs are around IE not shutting down when Outlook shuts down.

What we found in our investigation:

Our original attempt to fix the bug here really did fix it - for a brand new machine. One side effect of the original bug was that it toggled the setting for osf-roaming.16 under HKCU\Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\ProtocolDefaults from the original default of 3 (Internet Zone) to 4 (Restricted Zone). And on machines where this setting had been toggled from 3 to 4, our original fix was ineffective. The new fix takes all this in to account.

So - if you're still seeing orphaned IE processes and want to try to fix it NOW, you can toggle the value for osf-roaming.16 under HKCU\Computer\HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\ProtocolDefaults back to the default of 3. Otherwise, it looks like the next build of Insider Fast will likely have this fix in it.

I, too, was encountering terrible performance with Outlook in the last week and especially the last few days.

We connect to Exchange Online and have used the Dynamics 365 COM add-in.

Upon starting Outlook, we would see up to 6 IE threads start under Outlook (3 - 32 Bit and 3 non-identified)

We disabled the COM add-in and Outlook instantly began performing much better and the IE instances DID NOT start.

Not sure if this is relevant to your issue but, an FYI!

Still needs resolution, as we use the Dynamics add in for attaching emails to cases, etc...

We're seeing that here as well (I reprod on 16.0.10815.20000). It doesn't appear to repro if protected mode is set to the defaults. Dev is investigating.

I subscribed to Office 365 two days ago and installed it on Win 10 and Win 7.  I have the problem on both machines.

 1212  iexplore          Office Preload - Internet Explorer

 1832  iexplore          Office Preload - Internet Explorer

It has been 16 months since this thread was started and there has been no proper fix and no explanation of why the behavior is necessary.