Here is the running script:
#include <IE.au3>
Local $oIE = _IEAttach('https://outlook.office.com/owa/', 'url')
Sleep(8000)
_IENavigate($oIE, 'https://login.microsoftonline.com/logout.srf')
But it is hanging if using "Local $oIE = _IEAttach('https://outlook.office.com/owa/', 'url')"
Actually, after sending logoff url, clicking back once, still logoff page; clicking back twice, will back to inbox; keep clicking back button, takes me to the logon page, but if I click a the pre-configured Office 365 favorite link, I am in again. I don't have the issue if clicking Sign Out from OWA page.