Your company plans to migrate from On-Premises Exchange to Office 365. The existing directory
has numerous service accounts in your On-Premises Windows Active Directory (AD), stored in
separate AD Organizational Units (OU) for user accounts. You need to prevent the service
accounts in Windows AD from syncing with Azure AD. What should you do?

A.
Create an OU filter in the Azure AD Module for Windows PowerShell.

B.
Configure directory partitions in miisclient.exe.

C.
Set Active Directory ACLs to deny the DirSync Windows AD service account MSOL_AD_SYNC access to the
service account OUs.

D.
Create an OU filter in the Azure Management Portal.

Explanation:
One customer, who was looking for OU level filtering to import selected users from On-Premises
active directory to Office365. Configure OU level filtering for Office365 directory synchronization.
1. Logged in to your Domain controller
2. Created an OU (Organisational Unit) from your AD (Active Directory) a. In my case I named it
“DirSync”
3. Move all those users you want to sync, to that DirSync OU
4. From your DirSync Server navigate to <Drive>\\Program Files\\Microsoft Online Directory
Sync\\SYNCBUS\\Synchronization Service\\UIShell
5. Double click on miisclient.exe
……
http://blogs.msdn.com/b/denotation/archive/2012/11/21/installing-and-configure-dirsync-with-oulevel-filtering-for-office365.aspx