Mail Issue?

Hello. I have a server running Server 2003. It is on the domain but is not the exchange server. It has a small program that is supposed to use email (via Exchange account) to mail out an auto-generated report to internal and external email addresses. The internal email goes out fine but the external get the following error:

Sorry, your message to [email protected] could not be delivered.

The specific error is:
The following recipients are unknown: [email protected]
(made-up email of course!)

I can use this account to email out just fine if I use Outlook, but it will not send out external email otherwise, so it should not be an issue with the Exchange account or rights. Any help fixing this would be very much appreciated!

Thanks!

I deleted your other thread, Schtude you should know by now not to post the same question twice!!

So you are saying that emailing to any external mail address (which you know to be valid and working) produces that error message?

What is this "small program"?

I know...I just thought it might be in the wrong area after thinking about it!

Yes, the external emails are the ones that error out. I have confirmed that these are valid and have actually used Outlook with the same account to send test messages to those external addresses (it works with Outlook).

Thanks!

So what is the "small program" it doesn't work with?

A part of our warehouse management software. It is supposed to send out the auto-generated report. It does send out the report, the internal email accounts get it but the external ones bounce. Since this is on a different server than Exchange, I was wondering if something could be blocking external mail on the server, port issue, service, security restriction etc.

It could be any of those, or even a shortcoming of this management software that it can't use exchange...?