We are using exchange 2010 server.
1. User is in remote location (using outlook 2003)
2. User is able to send and receive internal emails(internal domain)
3. User is able to receive external emails
4. User is unable to send external emails and receives an NDR stating as below:
Your message did not reach some or all of the intended recipients.
Subject: This email is for testing purpose only
Sent: 02-11-2011 16:01
The following recipient(s) could not be reached:Raja, Rocket on 02-11-2011 16:01
550 5.7.1 Unable to relay