OWA outbound works but in outlook outbound doesn't work

[Omnicef]

I am having this problem...

I have an IIS in DMZ. It is also an exchange server. Using Outlook web access, I can send and receive e-mail just fine. But when I use outlook, I can only receive e-mail. I get an error message...

"No transport provider was available for delivery to this recipient."

I am running 2k exchange on 2k server.
Any ideas?

 

[robbyb]

At a guess, this might have something to do with your DMZ. On the Internet facing side, port 80 is open, and so you can connect with OWA. Port 25 is also open, so you can send with OWA.

With Outlook being on the Network side, you have somehow authenticated with the Exchange Server inside the DMZ (perhaps a path to the Exchange Server was opened up on the firewall).

But it might be that port 25 is blocked on the network side, and so you can't send from Outlook?