OK simple explanation.

Connect your BB to desk PC or laptop where you have or you need to install BB software DESKTOP MANAGER.

In main menu you will find ICON
EMAIL SETTINGS

General and EMAIL message redirection

you need to CHECK ( Forward incoming email messages to my device and click APPLY.

Then restart your BB and if this not work

then delete all account in BB unit.

How you do this :

Menu, Options, Advanced options, service book and
in service book find

2 times must be your email !!!

Mark one by one and with MENU button BB,
choose DELETE.

Restart BB.

Go to your Yahoo plus account mail on normal PC or laptop, go to OPTIONS find account settings and
CHANGE YOUR PASSWORD. (believe or not this will help
to me and many others what I help.)

After you change your password continue with NEW
installation of your Yahoo Plus email on BB like this:

Go to BB Menu on your unit (in my case is BOLD 9500)
and go to SETUP, then E-MAIL setup or you can do this step more easy from your home PC or laptop going to link:

http://qtel.blackberry.com/

Here if you are not registered make new account name,
then follow procedure so simple.

Hope that this will help you if not
cafe time in Villagio and we fix.

Best regards

Sun Fun Sea