One of my users connects to a SBS 2003 box over VPN (SBS Box runs the VPN server and they obtain local IP on LAN subnet) and uses Exchange through Outlook.
Recently, to some. but not all domains they have been getting error code 5.7.1 (unable to relay). In the relaying restrictions in Exchange i have the whole local LAN subnet as well as our WAN Subnet. I have also checked the DNS servers where we use ours and the ISP's.
The user in question has also been able to regularly email this address in the past with no problems.
Can anyone point me in the right direction on how to resolve this?!