did not receive out of office reply

I’m using Outlook 2003. I enabled the Out of Office Assistant. I discovered that only my colleagues receive the out of office reply but not for external parties.
I have done a test myself by using Outlook 2003 to send to myself and using Hotmail to send to my office email address. True enough, I receive the out of office reply from my office email but not in Hotmail.

Please advise

regards,