Question: How did you solve it?
while i'm waiting for this thread's reply. i'm trying to search google at the same time , and i found the solution in microsoft kb's (the second link exactly) . and i put my client's ip in the Relay restictions .

But all the message trying to send is return by the demon.

:
" Delivery to the following recipents failed.

[email protected]
"
i made sure the email is valid and my SMTP server can connect to Internet with properly configured DNS lookup.


i search the google around and come up with these questions :

1. what's the Smart host ?
2. Can IIS SMTP Virtual server send E-mails without forwarding them to Smart host?
3. If can how to configure it ? or how to test if it can send email?
4. May be it's because of firewall ? because my SMTP server is under heavily firewall, so i need to know whichports exactly need to be opened beside port 25, both incoming and outgoing.