Had the same problem but after logging onto yahoo & enabling POPed in my yahoo mail account (as jzaumu advised above) from: Options > Mail options > POP & Forwarding > Allow your Yahoo! Mail to be POPed > Save Changes. Then clicking the blue square help [?], & then Yahoo! Mail POP/SMTP Settings > POP Yahoo! Mail Plus with Another Email Client. I copied those settings in my phone, it all started working fine now. Now all I've got to do is get my yahoo messenger to work on my phone.