For some reasons, my mail server has been denied by yahoo smtp server, I can not send email to yahoo.com domain, the mail log is something like this :
B078B14A8008: email@example.com, relay=mta5.am0.yahoodns.net[22.214.171.124]:25, delay=2.9, delays=0.04/0/0.78/2.1, dsn=5.0.0, status=bounced (host mta5.am0.yahoodns.net[126.96.36.199] said: 554 Message not allowed - [PH01] Email not accepted for policy reasons. Please visit http://postmaster.yahoo.com/errors/postmaster-27.html  (in reply to end of DATA command))
I have tried changing my mail server using another IP but no luck. I also tried contacting with yahoo webmaster but no responses.