Problems with emails sent to Yahoo addresses

[Tyndaleon]

This may well be a host-specific issue rather than SMF, but I basically have a new SMF 2.0 forum setup and during testing registration via email validation, have discovered that nothing I send to Yahoo email addresses gets through at all to the account, not being sent to Spam or anything.  I've used the testmail.php script and verified I could send to Gmail or Hotmail for example without issue.  I also have tried using SMTP with a Gmail account instead of PHP, with the same results (can reach other email services, but not Yahoo). 

Based on the above information, does this sound like a host-specific issue, or could there still be a problem with some setting within SMF?  And if it sounds like a host-specific issue, does anyone have any advice on how I should approach them or what I should tell them to minimize potential run-around or back-and-forth communication and possibly get the problem resolved sooner?  Thanks in advance!

[Tyndaleon]

I should probably add if this factors in, I do have both StopSpammer and httpBL installed and setup properly, I wasn't sure if one of those might be causing the problem as I've read there are issues with Yahoo email and spam.

[Ricky.]

Yahoo is choosy when accepting mails. Issue is with your server, neither with SMF or Yahoo. You have to make sure that your server meets all requirements of a legit email server. You can find more about it at :
http://help.yahoo.com/l/us/yahoo/mail/postmaster/basics/;_ylt=AngL_MF.h5ouNCHAo7MjF3yiNCV4