I have been down since Thursday on my EVO 3D. Here is my response from yahoo:
Hello Chris,
Thank you for writing to Yahoo! Mobile.
I understand that you have recently stopped receiving mail in the
default mail application on your Android device, though the messages
still arrive in your Yahoo! account. I have given the information you
provided to our Mobile Product Team. Investigating and resolving this
issue may take some time.
Your ticket number for this issue is xxxxx. Please refer to this
number in any future correspondence regarding this issue.
You don't need a plus account because we are going to fix this.
It appears that both the Yahoo! Mail application and the Yahoo! Mobile
Mail page are unaffected by this issue. As a work around I recommend you
visit:
Login
You can either access your email directly from here, or download the
application via the link presented on this page while we work to resolve
this issue for you. You can also download the application via the
Android Market.
I have been using the K-9 app to get my yahoo mail. Its way better that the battery sucking yahoo mail app.