Emails are not delivered to external email addresses

I have successfully created a XML Bursting control file and was able to receive emails to my company email addresses. But when I run the program to send email to external email addresses, the bursting program completes normal with status 'Success' in the log, but the email is not delivered. I am sure this has some thing to do with our exchange server setup but wanted to check. The from email address I use is the same address I use from my other custom programs(unix scripts) from which I am sending emails of concurrent request output to our customers.