[H] Cox blocking

[Winterlight]

Why does Cox block customer service email? They have been doing this 
a long time. I can't reply with Eudora to anything from any tech 
support, or customer service, or anything like that. It gets blocked 
by COX SMTP server. I end up having to send from a web interface. It 
doesn't matter if I am sending to a big company like Logitech or a 
email vendor ,..... I have the same

Can't send to ''.  The server gives this reason: '553 Sorry, that 
domain isn't in my list of allowed rcpthosts.'.

error in Eudora.