[CentOS] Some best practices when sending to Yahoo! Mail

There were a ton of replies to the DKIM thread so I thought I'd chip in
with what Yahoo have stated on their website, 

Q What are some best practices when sending to Yahoo! Mail?
A http://help.yahoo.com/l/us/yahoo/mail/postmaster/postmaster-15.html

Apologies if this has been mentioned before in the 300 or so replies to 
that topic but problems sending mail to Yahoo, AOL, Hotmail are best served,
by looking at the FAQ's for those service providers. Believe me you are not
the first to have asked that question.

Thanks,
Josh.