Verified answer

Yahoo is aware of the problem, but so far they weren't able to fix it:

http://uk.answers.yahoo.com/question/index;_ylt=Ao...

Workaround for now: switch to Basic Mail - sign in to Yahoo! Mail, move your cursor over the gear icon top right and select mail options. Scroll all the way down on the "general" options page, check "basic mail", click save. There have been reports by other users that this works...

I have the same problem, I get code 45 and I go to the "help link" but so what!!! No response, no indication that my plea for help was send or heard... I've been with yahoo since 2002, but I will change quickly to gmail if I get no help on this... I rely on my emails...

I phoned them and the girl hardly spoke English and was rude... after being with yahoo for more than 13 years, this is driving me away rapidly...