exchange 2000

I don’t know why but for some wired reason we can’t send e-mails to the Yahoo domain from our exchange server when we use pop3 (smpt) either from outside the network or inside. but when we use OWA (out look web access) and regular outlook that is connected to the exchage server. we are fine.

we get the e-mails bounced back from the server with this error massage: (i have checked and all the e-mails that we send to exist so that should not be the problem)

did not reach the following recipient(s):
*****@yahoo.com on Thu, 22 Aug 2002 11:14:52 -0700
The e-mail account does not exist at the organization this message was sent to. Check the e-mail address, or contact the recipient directly to find out the correct address.