In 2013, Microsoft Outlook´s Cloud Business Development Manager - Benoît Roumagère - acknowledged that 2% - 3% of unwanted and unsafe emails avoid being detected by EOP. A subsequent test conducted by AV-Comparatives in 2016 rated Microsoft Outlook the worst performing of ten spam filters, after it detected just 89.87% of sophisticated spam emails. So, yes. It is really that bad at detecting spam.