How can we exclude external users from people picker in SharePoint Online

Is it possible to exclude / hide the external or guests accounts form the people picker in the share forms. We want to invite customers to some of our sites but we do not want their account to show up when we use the share dialog.

Only thing I found so far is to add a query rule to the "Local People results".

https://englando.wordpress.com/2015/07/24/hiding-users-from-office-365-sharepoint-global-search-results/ but I have not tried it yet.

It should be easy to do by flipping a tenant or site collection switch. With the external sharing now possible in Groups; Teams and Sites, I think it must be manageable.

Thanks,