I am using Outlook 2007.
Can't figure out why I can send some emails within my company... but anything to another email address will not work.

This is my "Undeliverable" email return message from "System Administrator"

Your message did not reach some or all of the intended recipients.

Subject: Test
Sent: 7/14/2011 11:31 AM

The following recipient(s) cannot be reached:

'test@email.com' on 7/14/2011 11:31 AM
550 #5.1.0 Address rejected test@email.com

***I have tried selecting "My outgoing server (SMTP) requires authentication"...

Please help!!!