Is it possible to prevent external users from finding other external users?
I'd like for the external users accessing to be unaware of each other and unable to find out the names of other external users.
While I could certainly use a custom css file to hide the this button it doesn't really solve the problem as internal users should be able to invite external users and share freely. I would just like to prevent external users from even accessing these dialogs.
Edit: After going into the permission group settings, I've made changes so that only members can view other members. In the screenshot above, the Shared with dialog will only show an external users other external users in the same permission group. However, if an external user searches in the Invite people dialog, they can still see other external users.
Edit2: I received an answer from Microsoft Support. Officially, kesava's answer below is correct. There is no OOTB way to prevent users not showing up in search even though the permission groups settings have been set to indicate that we don't want them to. Seems like another case of SharePoint getting 90% of where we want to be. At least there is an answer...