I found the problem ... I logged into the smtp service using telnet.
using: telnet localhost 25 -- everything worked fine.
using: telnet xyz.com 25 -- I got 550 5.0.0 Access denied when I did anything.
The problem -- I hadn't removed the /etc/hosts.allow & /etc/hosts.deny files.
Once I did it happily talked to any host that wanted to send me mail.
Duh !!
Cliff Kennedy