All the users in domain are not available to import.

When we are running Active Directory Import Wizard in Microsoft Dynamics AX. All the users in domain might not be available to import.

Link below is the solution for the same.

https://blogs.msdn.microsoft.com/axsupport/2016/11/01/cannot-see-all-users-on-the-domain-in-active-directory-import-wizard/

Below steps are described on above mentioned link.

1. In Active Directory Users and Computers, make sure that Advanced Features is selected under the View menu option.
2. Right-click the user that you cannot see when you run the import wizard. Then, select Properties.
3. Click the Security tab.
4. Click Authenticated Users group.
5. Click the Advanced button.
6. Select Authenticated Users name, and then click Edit.
   
7. Make sure that the Type is set to Allow and that the Applies to: box is set to This object and all descendant objects.
8. Make sure Read all.

Properties check box in Properties section is checked.