I am a NEWBIE so please have patience.
We just set up a new DELL system.
Powerconnect to Firebox SOHO 6 to Server, 4 workstations.
Server is running MS Small Business Server 2003, workstations are running MS XP Pro.

Problem now after we got through all the others, is that

running MS Exchange on Server for mail. Using Outlook on workstations. Outgoing mail is being blocked. Receiving messages back from AOL, Earthlink, DELL.com, HP.com etc

"message cannont be delivered due to a configuration erron on the server. Contact your Adminstrator. <pacbell.net #5.3.0 smtp. 553.5.3.0 DNSBL: To request removal of IP address please send an email to abuse@prodigy.net.>

Dynamic IP from ISP

income: pop.pacbell.yahoo.com
outgoing: smtp.pacbell.yahoo.com

On the DUL list!

How do we configure Exchange to work around this problem?

All replies are welcome!!