*Update*

ITS has restarted the ADFS login servers and contacted Microsoft for further assistance. Most users are able to login after clearing the browser cache or if that fails, trying another browser.
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Previous Description (2015-05-08 11:09:17):

ITS is investigating an issue with logins to Office 365 (Email, calendar and OneDrive services) where the login process is caught in a loop between the Queen's login page and Microsoft's. Clearing the browser cache has helped some users.