i think i’ve previously noted this, but i will do so again. office365 does not really allow you to alter a federated user and in some scenarios this can be frustrating. to retrieve the immutableid of an office365 user: get-msoluser -userprincipalname [upn] | fl to blank out the immutable id of a user: set-msoluser -userprincipalname […]

the browse/search OUs listing when creating a new user is blank. solution: edit c:\program files\microsoft\exchange server\v15\clientaccess\ecp\web.config on servers holding the CAS role. adding following entry: add key=”GetListDefaultResultSize” value=”1000″ source: https://social.technet.microsoft.com/Forums/exchange/en-US/15b66332-16e5-4c76-a84d-a4221ffa43dc/not-able-to-see-all-organizational-units-when-trying-to-create-mail-objects-in-ecp?forum=exchangesvradmin