To give you a false sense of security, there is a setting in the Office 365 Exchange Management Console to disable “User owned Apps and Services” with options for “Let people in your organization go to the Office Store” and “Let users install trial apps and services”. However, all that does it block access to the Office Store when staff surf directly to the web page STORE.OFFICE.COM and try to install something. It does not disable the GET ADD-INS button and it does not stop users from installing add-ins.
After digging through many posts and suggestions I gave up and worked with Microsoft support for about a week. Eventually, they came up with a registry entry that functions. I have tested in on both Outlook 2016 and 2019.
reg add HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Options\Webext /v StoreButtonInRibbonHomeTabAllowed /t reg_dword /d 0 /f
- Launch Group Policy Management Console (GPMC)
- Create a new GPO or edit an existing one
- Expand USER CONFIGURATION > PREFERENCES > WINDOWS SETTINGS > REGISTRY
- Right click in the blank space in the REGISTRY pane and select NEW > REGISTRY ITEM
- Set ACTIONS to UPDATE
- Set HIVE to HKEY_CURRENT_USER
- Set KEY PATH to
- Set VALUE NAME to
- Set VALUE TYPE to REG_DWORD
- Set VALUE DATA to 0 (zero) and click OK to finish
Close Outlook and force a replication use GPUDATE /FORCE (not as an Admin because this is a local user) or reboot and you will see that the GET ADD-INS button is not just disabled, it is removed all together. Note that we have noticed that the first time Outlook is started it takes an extra minute or two, which is very strange but acceptable.