Whenever i reply to peoples email, 60% of the time i get a bounce back that says the following...

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

Subject: RE: Advertising inquiry
Sent: 7/31/2007 2:17 PM

The following recipient(s) cannot be reached:

'Chris Cheuvront' on 7/31/2007 2:18 PM
513 Relaying denied.
Anyone know what the reason for this is?

Im using OutLook 2007.

Regards,

Lee