outlook redirecting to wrong site

At the university I have just graduated from, we used Outlook to access the university email system (through outlook web app). I have now joined a new university who also do this, but whenever i try to log in to the new university email account, I automatically get directed to the login page for the old university account. I have tried the basics- restarting the browser, deleting all cookies etc. but I still cannot access the new email system. Does anyone have any ideas?

I don't know if it has anything to do with it, but the URL address for the old uni email has CookieAuth.dll in it, I can access other email systems through outlook just fine that do not have the CookieAuth.dll part. 

Thanks for your help!