By default, Microsoft Exchange Server 2003 Out-of-Office replies to the Internet is disabled. This is done to disallow Out-of-Office auto-replies to be sent outside of the organization to prevent outsider to learn when users are out of the office.
To enable Out-Of-Office replies to the Internet:
1. On the Exchange Server machine, go to Start - Programs - Microsoft Exchange - Systems Manager.
2. Double click Global Settings, and then click Internet Message Formats.