HowTo Filter users synced to Office 365.
Open your Synchronization Service Manager: C:Program FilesMicrosoft Online Directory SyncSYNCBUSSynchronization ServiceUIShellmiisclient.exe
From here we can do several filtering, but I will show the most used filtering which is from Organizational Units.
Choose your domain forest level and click on Containers… You will be asked for password to the service account named MIIS_Service, which is created by the DirSync Configuration and we do not know the password of this user. So just change the credentials with your own Domain Admin credentials.
You will then be presented with your Active Directory hierarchy and can choose which Organizational Units to include in synchronization to Office 365.
Otherweis you can filter on allmost any attribute in your Active Directyr User Object. Might to another article on that later.