Filters with Multiple Email Accounts - Impossible to set up
Filters - Filters in the Classic Mail were fantastic - super simple to implement and I had a LOT of them (to the point my inbox was clean, containing the important emails only). The upgrade removed ALL of my filters - and creating new ones can only be done in the settings menu. I have multiple emails (a business email account and personal) linked to a single account - the business one doesn't even list its own folders in the new filters option in settings (yet I am clicking on settings from that account). I am very close to moving providers after being a 20 year PAYING business Yahoo customer. Please be sure to enhance filters in the next release. I love the other new features, but the filters are a game changer for me!

Filters have to be set separately for each account and mailbox. https://help.yahoo.com/kb/new-mail-for-desktop/sln28071.html