Vodamail web login issues

When I log in successfully into my vodamail on the internet browser vodamail website and click on inbox it just kicks me out to the log in page all the time. I can login but cannot do anything without being kicked out.

My e mails are working fine on my laptop in Microsoft Outlook. But why am i having issues on the webpage login page itself (vodamail.secure.vodacom.co.za/vodamail_ui/?skipsso=true#home)