Fix e-mail server spam problem when sent to Yahoo Mail

Hello There, I am a freelancer like you too. :) Its great work here with GAF. Ok, the project is I have a serious problem regarding site, when we send legitimate emails from this domain the e-mails goes to spam box in yahoo and works good with gmail and hotmail. We want this to be fixed. If you are certain you can fix this job please place a bid with keyword DOABLE. We have plesk 8.4 + qmail + domain keys + spf records And all the above are tested and verified successfully. We are not able to figure out whats wrong with our email. Important thing is we dont spam users. we send emails for the users registered with us. But, still marked spam.