When I first saw this thread I thought it was old news since I heard about
port 25 blocking quite some time ago. But I think they have put in some
active filtering of outgoing mail now. Previously I could still send email
to any address using a PHP script on Apache by including the following in my
virtual host definition:

php_admin_value sendmail_path "/usr/sbin/sendmail -t -i -f name@domain.xxx"

-where domain.xxx was a valid domain name. It was handy for testing PHP
programs that automatically send email. But now after a couple of hours of
testing and fiddle-dicking around I find I can only send to my own cox email
address using this method. One alternative I discovered is to send to an
account on the same host as Apache/PHP. Lucky for me I don't have any
spamish intentions, or I'd be shut down. A little annoying, but if it cuts
down on spam I guess I can live with it. But after using SpamCop for a while
I've noticed that a lot of spam comes from China, Eastern Europe and other
crud-holes like that. Cox is just covering their own butt.
--Phil M.