All AD users is visible in people picker in central administration in sharepoint 2013 but in web applictions it's not visible,if i use user's emailid it shows "Sorry,you are not allowed to share this with external users."(Using SP on premises-Not online)

Please help...can't share my web app to any of the user

I have Different OU's in my AD but I want that my web application will read all users from all OU's & I thought it is by default until and unless we don't restrict by using some PowerShell commands.

But my web application is reading the users in people picker which resides on my Company OU, and not showing any of the users on other OU's