more confirmation that others are experiencing this problem and that yahoo is at least trying to work on solving it:
The Email Delivery Guru - Yahoo Issues
its not much help, but there is this related blog entry on the spamhaus site now
http://www.spamhaus.org/news.lasso?article=644
its basically saying there's nothing wrong on the spamhaus side and if your IP address is not listed in Spamhaus blacklist , then there is nothing spamhaus can...
we're a jobs website in Asia and we do about 1.5 - 2million emails a day (mostly job opportunity alert emails).. I have done the bulk mail declaration in the past... but not the particular form you mentioned...(yahoo's had several iterations of this declaration, i don't bother to keep...
Re: Yahoo Intermittent and Erroneous IP Based blocks
Thanks for posting this... i've also been experiencing this for about 20 -30% of our deliveries to the yahoo domain since about the 22nd of may 2009...