Outlook 2003 on XP2 workstations will receive email but will not send. Oddly, it will "reply" to some received email but will fail to send a new composed email. We receive the following NDR report:
The following recipient(s) could not be reached:
email@example.com on 2/6/2008 12:30 PM
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<ourdomain.com #5.5.0 smtp;550 relaying mail to yahoo.com is not allowed>
We get this report sending to various domains including earthlink, yahoo, and others. Our incoming email comes in fine and is retrieved pop3 from our domain hosting mail server. Our SMTP outgoing server is configured to our provider "smtp.att.yahoo.com" which required authentication using our provider email address and password on incoming port 110 and outgoing port 465.
I have spent many hours now, including a couple of hours with SBC yahoo tech support and have been unable to remedy. SBC yahoo advised the problem must be within our local network. Any advice would be greatly appreciated!