Brand new 10.10 Yosemite mail.app can not work with Yahoo Mail

As of January 2015, I have a brand new Macbook Air running all fully updated Yosemite 10.10.

I have been simply trying to configure the mac OS mail app to work with a simple, normal Yahoo Mail account.

I add the account, it appears correctly in the Preferences settings as an internet account with "mail" checked… it creates entries in the left pane of the Mail window. BUT… nothing ever appears in the Inbox. AND, it DOES succeed in loading the many sub-folders within the mail account that I have configured in yahoo… AND, if I click on one of those, then after 20 seconds, it loads the folder's contents fine. AND, when I SEND mail, it sends out just fine. But nothing in the normal, plain Inbox!

I have created it several times. Once I even tried to force it to allow me to "manually" create the inbox without it sniffing that it was a yahoo account and applying the official yahoo settings it knows. I did that by initially putting extra false characters in the yahoo domain name, and then setting up all the IMAP and SMTP stuff manually, and then changing the initial domain name entry to remove the wrong characters. But the results were exactly the same — empty inbox.

AND, when I have yahoo set up in the normal way (but not working right…) and I go to the Connection Doctor… it scans through and gives the green-light indicator saying that IMAP and SMTP are working fine!

Any info, tips, or similar issues with Yahoo Mail and the mail.app in Yosemite?

THANKS — Eric