Introducing an extra line in the local gateways which included the host name did the trick for me using a POP client. The Mac became magically verifible the upstream SMTP server was happy.
People using the TF Client wern't so happy as all there E-Mail's now had a return address which included the node name of the TF MailServer.
Changing the Gateway entry to the correct domain name cured the problem but returned the problem with the Mac being Unverifible
