Configuration Problem

My domain is hosted by yahoo.  Outside of yahoo, I use another
outbound mail server.

My goal is to designate yahoo's smtp server and my outbound server as
the only legitimate outbound server.

My spf configuration is as follows:

"v=spf1 a:smtp.bizmail.yahoo.com ip4:XX.XXX.XXX.XX -all"     where my
server is XX.XXX.XXX.XX.

This configuration works for my server but not yahoo.  I am guessing
the problem is smtp.bizmail.yahoo.com cname.

I spoke with yahoo..  They are not providing me with ip ranges or subnets.

Is there a way to make this work or, perhaps, someone may have done
this already.


Thanks in advance