You'll first need to install the VSTO runtime.
Remove all existing versions of OutlookCloseToMinimize.
Then double-click OutlookCloseToMinimize.msi.
The addin works best when the "Hide when minimized" option is enabled (by right-clicking Outlook's tray icon):
If Outlook crashes, simply run outlook.exe /safe and remove the addin manually from Options - Add-ins.
Apply the included Registry file: forceload.reg (right-click - Save link as...)
Licensed under GPL version 3.
I tested the addin with Outlook 365 and .NET 4.7.2, but in theory it should work with older Outlook versions with no problem.