SMTP Not Working

[Atomic Frog]

	My SMTP doesn't seem to be working anymore. I used to grab
things from my POP server and send them off via SMTP, however, it
stopped working in the past few weeks. I don't believe I've made a
change in my settings.

I get this typical error message in the log:

Thu, 23 Sep 99 18:10:39 ==> 550 <bigjoe@joes_company.com>... Relaying
denied ; This is the error that resulted from the RCPT TO command

Sending via POP still works. As does SMTP, if I send to another
recipient with the same domain, but not outside.

For example, my mail server is: mail.isp-host.com
If I send to myself or another user @isp-host.com using SMTP, it's
fine. As soon as I try an address outside the site, I get the error
described above.

Can anyone tell me if this is a problem in my PMMail setup or my ISP
problem?
I have it using the default Port 25 on SMTP.


Thanks for any help,
Isaac