Hi Folks,
I used to work for Yahoo! supporting (you guessed it) Yahoo! Mail. I have reliable contacts working for the Yahoo! Mail and SpamGuard teams and I know where and how to get these things resolved. I've emailed Armagan for additional details, as I wasn't aware of the delivery issue until today (my bad for not following the forums for over 6 months). Once I have some details from Armagan, I'll try to help get this straightened. We can't simply hold our breath and ignore the largest email service provider in the world.
I also want to note that this will impact certain ISP email services as well, as Yahoo! Mail is co-branded with several large ISPs in the U.S., Canada, and New Zealand. I can't say specifically which ones are or aren't affected, but I can clearly point out that the other two contenders, Hotmail/Live Mail and Gmail, shouldn't generally be affected. In many similar email systems, however, the same antispam mechanisms may also be triggered and cause unpredictable delivery issues or SMTP deferment issues.
In the meantime, I'd suggest using an alternate email service provider until the delivery issue can be resolved.
Thanks.