Exchange server not sending mail outside domain from web application

[syukna]

Hi:

I have a web application that can send email within our domain without any issues. Sending emails outside of the domain does not throw an error in our web application (ie: unresolved address), but the intended recipient does not receive the email. We have logged onto the web server directly and sent an email sucessfully using Outlook Express to remove the possibility of it being a firewall issue.

I understand Exchange Server is very complex, and not having much experience is making this a trying issue for me. I guess if anyone has any ideas of what the issue could be or areas I could check within Exchange Server (I'm sure this problem could be a bunch of things). Also if anyone knows of literature that describes the protocols between a web application and exchange server so I can try and narrow the problem down myself.

Thanks so much for any help anyone can give me.

 

[Zelandakh]

You'd need to get Exchange to allow relaying from that IP address. What does Event log say on either server?

 

[syukna]

Relaying is allowed. I can send mail through command prompt and outlook express. I'm running out of ideas... :-\

 

[syukna]

I ended up being an issue with our exchange server not allowing emails to be sent out from an email address that doesn't exist.

Thanks for the help Zel