Yahoo window keeps asking me to sign in to currently.com account in Outlook

I've had my Outlook 365 running perfectly for years until this week. Suddenly, whenever I open Outlook a YAHOO window opens up asking me to sign into my currently account. I do NOT want currently to have anything to do with Outlook. How do I stop YAHOO from asking me to sign into my currently account every time I open Outlook? When I close the YAHOO window, it just keeps opening up again, rendering Outlook useless. It is very annoying.