on the "Help for Yahoo Mail" page

https://help.yahoo.com/kb/mail-app-for-android?redirect=true

select "Fix problems with Android apps"

https://help.yahoo.com/kb/mail-app-for-android/fix-problems-android-apps-sln14699.html

click on "Feature unavailable on mobile device" link

click on "Yahoo features not available on mobile devices." link

https://help.yahoo.com/kb/mail-app-for-android/yahoo-features-mobile-devices-sln2704.html

Taken back to Help for Yahoo Mail page with error message

You have been redirected to this page because the page you requested was not found.