It can be anything! An apex, subdomain, or even a URL.
Results forwww.activedirectory.windowsazure.com.office.rp-o365.agircarrco.myshn.eu
activedirectory.windowsazure.com.office.rp-o365.agircarrco.myshn.euwindowsazure.com.office.rp-o365.agircarrco.myshn.eucom.office.rp-o365.agircarrco.myshn.euoffice.rp-o365.agircarrco.myshn.eurp-o365.agircarrco.myshn.euagircarrco.myshn.eumyshn.eueu