Delete old computers from Active Directory

Get list of inactive computer for 4 weeks:
dsquery computer –inactive 4

Source: portal.sivarajan.com

Change Office 365 sign-in name for AD synced user

To change Office 365 sign-in (Principal) name for user synced with Onsite AD:

1. Start PowerShell
2. Make sure the Microsoft Online module is loaded
3. Execute the following command:

set-msoluserprincipalname -newuserprincipalname newuser@emailaddress.com -userprincipalname user@emailaddress.com.

Source: msonlinehelpdesk.zendesk.com