Linux Discussion Group

Hi All

I have w2k3 DCs and exchange 2003. I have a linux server that runs
discussion group.
The discussion group is able to send messages to the user community
but when they reply back - it mails doesnt go the linux server.
(Discussion groups runs of JAMES 2.2.0--

Any thoughts as to what I can do?

I have users that have external address like ie yahoo, hotmail, and
external contracting companies

The user that have external email addy like hotmail gets 4.4.7 replies
back and yahoo :
Connected to ip but greeting failed.
Remote host said: 554 5.7.1 Connection not
authorized I'm not going to try again; this message has been in the
queue too

I've went through the firewall and okayed but still nothing...

On the exchange side do I create a new smtp virtual, do anything to
the recipient policy?
New connector?
.....actually i've everything but create a new smtp virtual --