Exchange 5.5 relay

question about internet mail relaying:

I closed off our exchange 5.5 server from relaying UCE mail. well, almost. The trouble is, it doesn't relay the mail, but it still accepts it. at any given time, i can look at my outbound queue in the exchange server, and find about 30 emails to dubious destinations, with "<>" as the Originator.

What's the best way to stop my server from even accepting these emails for delivery? Do have have to setup SMTP authentication?

Thanks!

SMTP authentication would probably be the most roebust solution. You can also setup the properties of the SMTP server to only accept connections by IP address etc........

I went with authentication and it works well. If you have dialup clients sending through your SMTP server it's tough to enable IP authentication and it's not as secure.